Thai

Letters

Combining marks

Numbers

Punctuation

Symbols

Other

Vowel sounds

Consonant sounds

	labial	dental	alveolar	post- alveolar	palatal	velar	glottal
stops	p b	t d				k	ʔ
	pʰ	tʰ				kʰ
affricates				t͡ɕ
				t͡ɕʰ
fricatives	f		s				h
nasals	m		n			ŋ
approximants	w		l		j
trills/flaps			r

Tone

Thai is a contour tone language, with 5 tones: high, mid, low, falling, & rising.

The following table provides typical phonological transcriptions and descriptions for the five tones.wl,#Tones

Structure

Thai syllables allow the following patterns, where V can be a short or a long vowelc,#Thai.

V VC CV CVC CCV CCVC

The long vs. short vowel distinction is phonemically important. Long vowels are approximately twice the length of short ones. All open syllables have long vowels.wl,#Vowel_developments

Consonant clusters only occur in syllable initial position, with the following permissable combinations:c,#Thai

• pʰr pʰl
• tʰr
• kʰr kʰl kʰw

Syllable-final consonants can be one of the following.c,#Thai Stops are unreleased.

-p̚ -t̚ -k̚ -m -n -ŋ -j -w

Vowel summary table

The following table summarises the main vowel to character assigments.

ⓘ represents the inherent vowel. Not listed here are 18 additional diphthongs (shown in the sections below) that are created by adding a -j or -w glide after vowels shown in this table. ◌ indicates the location of a consonant, but does not necessarily indicate a combining mark.

For additional details see vowel_mappings.

Inherent vowels

ก ko ~ ka ~ kɔː U+0E01 THAI CHARACTER KO KAI

The inherent vowel is pronounced o inside a closed syllable, and a in an open syllable. So ka can be written by simply using the consonant letter ก, and kon by just the 2 consonants, กน. Example of a single word using both inherent vowels:

ถนน

A third inherent vowel, ɔː, occurs before a syllable-final RA (which is pronounced n), eg.

ศร

นคร

Post-consonant vowels

กิ ki U+0E01 THAI CHARACTER KO KAI + U+0E34 THAI CHARACTER SARA I

Post-consonant vowel sounds are represented using combining marks, and vowel letters, including 4 consonants, very often combined into composite vowels. This page lists 37 composite vowels (including diphthongs), which can involve up to 4 glyphs (plus a tone mark) at a time, and can surround the base consonant(s) on up to 3 sides simultaneously.

Vowel sounds are often written differently when they appear in a closed vs. open syllable. Thai vowels all come in short and long forms, which are phonemically distinctive. Short vowels in open syllables usually end with a glottal stop. A set of diphthongs end in a̯, and most vowels can be followed by either w or j.

Thai uses visual placement: only the 8 vowel components that appear above or below the consonant are combining marks; the others are ordinary spacing characters that are typed in the order seen.

There are 5 pre-base vowel glyphs, but no circumgraphs, although the many composite vowel components often appear on more than one side of the base.

Pre-base vowel glyphs

โก koː U+0E42 THAI CHARACTER SARA O + U+0E01 THAI CHARACTER KO KAI

Five vowel glyphs appear to the left of the onset consonant(s).

เ␣แ␣ใ␣ไ␣โ

Since Thai uses a visual encoding model, these are not combining marks. They are typed and stored before the base.

Click on the following word to see the sequence of characters in storage.

ไข่

These vowel characters are actually placed before the start of the syllable. This means that a word with a consonant cluster at the start separates the pre-base vowel from any post-base vowels by more than one consonant character, eg.

เปล่า

fig_prebase graphically illustrates the arrangement of glyphs for the word program.

show composition

โปรแกรม

แ should not be typed as two successive เ characters (see encoding_sarah_ae).

Composite vowels

เกียะ kia̯ʔ U+0E40 SARA E + U+0E01 KO KA + U+0E35 SARA II + U+0E22 YO YAK + U+0E30 SARA A

This page lists 37 composite vowels (including diphthongs) made from 12 dedicated vowel characters, and 4 consonants. Composite vowels can involve up to 4 glyphs (plus a tone mark), and glyphs can surround the base consonant(s) on up to 3 sides.

show composition

เกี๊ยะ

Some represent plain vowel sounds:

ือ␣เ◌ะ␣เ◌็␣เ◌ิ␣เ◌อ␣เ◌อะ␣โ◌ะ␣็อ␣แ◌ะ␣แ◌็␣เ◌าะ

The other composite vowels represent diphthongs, which generally end in one of ə̯, i, or w.

For some, the spelling isn't completely obvious.

เ◌ีย␣เ◌ียะ␣เ◌ือ␣เ◌ือะ␣ัว␣ัวะ

In many other cases, a semivowel is simply added after one of the vowels seen earlier. See diphthongsz for a list.

Finally, the two vocalic letters can be lengthened using an additional, special character (see vocalics).

ฤๅ␣ฦๅ

Characters that don't appear in the combinations:

ร␣ำ␣ึ␣ใ

Show which combinations contain a given character:

ะ	เ◌ะ␣โ◌ะ␣แ◌ะ␣เ◌าะ␣เ◌อะ␣ ␣เ◌ียะ␣เ◌ือะ␣◌ัวะ
ั	◌ัย␣ ␣◌ัวะ␣◌ัว
า	เ◌าะ␣ ␣◌าย␣ ␣◌าว␣เ◌า
ิ	เ◌ิ␣ ␣◌ิว
ี	เ◌ีย␣เ◌ียะ␣ ␣เ◌ียว
ื	◌ือ␣ ␣เ◌ือ␣เ◌ือะ␣ ␣เ◌ือย
ุ	◌ุย
ู	◌ูย
เ	เ◌ะ␣เ◌็␣เ◌อ␣เ◌ิ␣เ◌าะ␣เ◌อะ␣ ␣เ◌ือ␣เ◌ีย␣เ◌ียะ␣เ◌ือะ␣ ␣เ◌ย␣เ◌ือย␣ ␣เ◌ว␣เ◌า␣เ◌็ว␣เ◌ียว
แ	แ◌ะ␣แ◌็␣ ␣แ◌ว
โ	โ◌ะ␣ ␣โ◌ย
ไ	ไ◌ย
็	◌็อ␣เ◌็␣แ◌็␣ ␣◌็อย␣ ␣เ◌็ว
อ	◌ือ␣◌็อ␣เ◌อ␣เ◌อะ␣ ␣เ◌ือ␣เ◌ือะ␣ ␣◌อย␣◌็อย␣เ◌ือย
ย	เ◌ีย␣เ◌ียะ␣ ␣◌ัย␣◌าย␣◌อย␣◌ุย␣◌ูย␣◌วย␣เ◌ย␣โ◌ย␣ไ◌ย␣◌็อย␣เ◌ือย␣ ␣เ◌ียว
ว	◌ัว␣◌ัวะ␣ ␣◌วย␣ ␣◌ิว␣◌าว␣เ◌ว␣แ◌ว␣เ◌็ว␣เ◌ียว
ร	◌รร◌␣◌รร

Show details about glyph positioning

The following list shows where vowel sign glyphs are positioned around a base consonant to produce vowels, and how many instances of that pattern there are. The figure after the + sign represents combinations of Unicode characters,

• 5 pre-base, eg. โก ok̯ (ko)
• 2 post-base, eg. กา k̯ā
• 5 superscript, eg. กิ k̯i
• 2 subscript, eg. กุ k̯u
• 1+5 sup+post-base, eg. กือ k̯ɯ̄ʔ̯ kɯːo
• +4 post+post-base, eg. กาว k̯āw̱ kaːw
• +2 sub+post-base, eg. กุย k̯uy̱ kuj
• +10 pre+post-base, eg. เกะ ek̯a kè
• +3 pre+superscript, eg. เกิ ek̯i kɤː
• +2 super+post+post, eg. กัวะ k̯äw̱a kua
• +2 pre+post+post, eg. เกาะ ek̯āa kɔ̀
• +3 pre+sup+post-base, eg. เกือ ek̯ɯ̄ʔ̯ kɯːa
• +4 pre+sup+post+post-base, eg. เกียะ ek̯īy̱a kiːa

At maximum, vowel components can occur concurrently on 3 sides of the base.

Distribution of vowel elements is as follows:

	ั   ิ   ี   ึ   ื   ็	ำ
เ แ ใ ไ โ		อ ะ า ย ว ๅ	ะ ย
	ุ   ู

Standalone vowels

Thai uses 0E2D as a base for vowel signs, eg.

อิ่ม

เออออ

สะอาด

อ on its own represents the same sound as the inherent vowel, eg. อเมริกา

There are no independent vowel letters in Thai,

Tones

Tone in Thai is indicated by a combination of the consonant class, the syllable type (live/dead), vowel length (for dead syllables), plus any tone mark.

Each onset consonant is associated with a 'high', 'mid', or 'low' class, which is related to, but not indicative of, tone. (For example, when they appear without tone marks the 'high' class consonants produce a rising tone, and 'mid' or 'low' class consonants both produce a mid tone.)

Tone is also affected by the use of the following combining marks on live syllables, however in 2 cases the result of their use is also context-dependent, due to historical linguistic changes. (For example, 0E48 can produce either a low tone or a falling tone, depending on the class of the onset.)

Vowel sounds mapped to characters

This section maps Thai vowel sounds to common graphemes in the Thai orthography.

The ◌ indicates the location of a consonant relative to the vowel sign; if there are 2 of these, the vowel is used only in closed syllables.

Click on a grapheme to find other mentions on this page (links appear at the bottom of the page). Click on the character name to see examples and for detailed descriptions of the character(s) shown.

Wiktionary provides a very useful table of Thai rhymes.

Consonant summary table

The following table summarises the main consonant to character assigments.

The first few rows are for initial consonants. They are split across high, mid, and low columns. The later rows are for syllable-final consonants.

For additional details see vowel_mappings.

Basic consonants

Whereas the table just above takes you from sounds to letters, the following simply lists the basic consonant letters.

Each of the basic consonants is associated with one of 3 classes (high, mid, and low), that play a part in indicating the tone of the syllable (see tones). In not all cases does this lead to more than one letter for a given consonant.

The pronunciation of a letter often differs when the consonant is the onset or coda of a syllable.

In the following lists, the class of each consonant is shown just below the IPA data. If a dash appears after the IPA transcription, it indicates the pronunciation in syllable-initial position; before indicates the pronunciation for syllable codas.

Onsets

Consonant letter clusters at the start of a syllable usually represent medial glides, tone markers, or an initial s.

Finals

Only the phonemes p, t, k, m, n, ŋ occur at the end of a syllable, however many more consonant letters can appear in final position.

The following consonant letters are pronounced differently in syllable-initial and syllable-final positions.

For example,0E25 in:

ลิง

ตำบล

Consonants at the end of a syllable use ordinary code points, eg.

ตื่น

This can create some ambiguity, since there is no distinction between the sequence in the previous example and one where น is a new syllable with an inherent vowel.

The one exception is the character that is normally regarded as a vowel but that in fact represents a rhyme: 0E33, which includes the final -m sound, eg.

ห้องน้ำ

However, a final -m is not always represented using sara am) eg. ห้าม

Consonant clusters

See onsets for consonant clusters that occur at the beginning of a syllable.

Otherwise, consonant letter clusters only occur where one syllable ends with a consonant and the next begins with one.

Thai doesn't have conjuncts, or any way of generally indicating where an inherent vowel is cancelled. As described in finals, this can lead to ambiguous parsing of text, since it's not clear whether a consonant represents a syllable coda or a new syllable with inherent vowel.

0E3A is used as a virama when writing Pali. It is not used in modern Thai.

Consonant length

The Thai orthography has no special features for dealing with geminated or long consonant sounds, however see also folding.

Consonant sounds mapped to characters

This section maps Thai consonant sounds to common graphemes in the Thai orthography.

Rows with 2 columns are high class and low class, respectively. For stop and affricate onsets, rows with a single, centred column are mid class.

Click on a grapheme to find other mentions on this page (links appear at the bottom of the page). Click on the character name to see examples and for detailed descriptions of the character(s) shown.

Cancellation mark

0E4C can be used above a consonant or syllable when it is not pronounced (usually at the end of a syllable).

Click on the words to see the pronunciation more clearly.

รถเมล์ศักดิ์สิทธิ์ It is often used for foreign loan words, eg. คอมพิวเตอร์ โปสการ์ด สแตมป์

SARA AE

In complex scripts, visually similar or identical glyph patterns can often be made from a sequence of code points rather than the single code point that Unicode provides. These are not made the same by normalisation, and they are not semantically equivalent. These inappropriate sequences should be avoided because they will cause the meaning of the text to change; searches, matching and other aspects of the text will fail to be understood by the application or the font.

Only one such is listed in the table below, The single code point on the left should be used, and not the sequence on the right. In some cases, fonts will indicate that there is a problem by forcing the appearance of a dotted circle or otherwise failing to render the text correctly, but this may not always be the case.

Nikahit

The combination of nikahit and sara aa is normally written with the precomposed character in the Thai block. It is possible to use 2 code points to create something that may visually look identical (and is in fact used during justification), but the single character and the sequence are not converted to each other during normalisation; therefore, the text will be read as different by normalisation-based matching algorithms.

Code point sequences

As already mentioned, Thai is visually encoded so pre-base glyphs are associated with ordinary spacing characters, and these need to be typed and stored in visual order relative to the base consonant(s) in a syllable. If the syllable begins with a consonant cluster such as pr, the pre-base code points must be typed before the p, even though they are pronounced after the r.

Tone marks should be typed and stored after any combining vowel mark. Fonts will typically indicate visually that the order is incorrect because the tone mark will appear below the vowel mark if they are the wrong way around.

Currency

The currency symbol for baht is encoded in the Unicode Thai block.

The CLDR standard format for currency is ¤#,##0.00.cldr

Dates

Thailand commonly uses the Buddhist Era calendar. The Gregorian year 2000 was 2543 in the Buddhist calendar.

In fig_thai_date the abbreviation พ.ศ. p̱ʰ.ś. stands for Buddhist era.

Font styles

Modern type styles often omit the loops found in more traditional typefaces. See an article that explores this in depth.

Loopless is considered to be more contemporary and modern, and is mainly used for advertising and titling. The distinction doesn’t necessarily map to that of serif vs sans – Noto, for example, provides both serif and sans Thai font faces, but they both have loops. On the other hand, Neue Frutiger Thai offers traditional (looped) and modern (loopless) alternatives as part of the same font family (each with both regular, italic and bold substyles).

Context-based shaping & positioning

Thai has no stacking or conjunct behaviour, but the following are a few selected examples of contextual shaping and positioning.

Most of the combining characters in Thai are used for vowel signs and tone marks. Combining characters need to be placed in different positions, according to the visual context. The example below shows the same tone character displayed at different heights, according to what falls beneath it.

Thai regularly combines multiple combining characters above a base consonant. There are two examples in the text below, both of which show a base character with a vowel sign and then a tone mark on top.

Although Thai has very little in the way of shaping, fig_shaping shows a number of small glyph adaptations that occur in some fonts (here, Noto Serif Thai) when certain tall or deep consonant letters have vowel marks attached. The 2 examples on the left show a slight reduction in the downward extent of the consonant glyph; in the middle 2 examples the part of the consonant glyph that lies below the baseline is removed altogether and replaced by the vowel sign; and in the right-most example, the height of the consonant glyph is reduced when a vowel sign appears above it.

Letterform slopes, weights, & italics

Ben Mitchell describes how italicisation is used for meta text and to convey the ‘about’ voice, rather than for emphasis or names of things (for which bold is used).

Italicisation tends to be applied to whole paragraphs or groups of paragraphs, for such things as picture captions, bylines, and other labels, commentaries, summaries such as standfirsts in magazines or news stories, and signposting. It is also regularly used for direct speech between quote marks.

Observation: Thai newspapers appear to use italic text for captions and by-lines. There is no evidence of the use of inline italicisation, but there is inline bolding.

Word boundaries

Thai doesn't separate words in a phrase.

Spaces are used in Thai as phrase separators, but Thai doesn't separate words in a phrase using visible spaces.

There is, however, a concept of words in the text. For example, lines are supposed to be broken at word boundaries.

Word boundary detection

The main difficulty arises when dealing with compound words. It can often be difficult to decide whether a given string of syllables represents multiple words or a single compound word.

The variation may be related to the operation being performed on the text (eg. line breaking in narrow newsprint columns, vs. double-click selection, vs. cursor movement, etc.), or it may just be down to personal preference,

The difference may also be contextually dependent. Wirote Aroonmanakun describes how คนขับรถ should be viewed as a single word in the context คนขับรถนั่งคอยอยู่ในรถ, whereas in the phrase คนขับรถผ่านแยกนี้ไม่มากนัก it would be viewed as 3 words, referring to anyone who is driving.at

Proper names, which are composed from multiple words, are also problematic, especially because there are no capital letters to distinguish them from other pieces of text.g2455,#issuecomment-375162188

Graphemes

Non-combining Thai vowel characters are treated as independent grapheme clusters. Only combining characters are grouped together with their base into a cluster.

Grapheme clusters

Base SARA_AM? Combining_mark*

Combining_mark may include zero or more of the following types of character, grouped by labels that correspond to Unicode Indic syllabic category values.

1. Dependent vowels [9] (see combiningV) Thai has many composite vowels that are made of combinations of ordinary letter characters and combining marks clustered around a base, but in the modern Thai language only one of these dependent vowels is used per base. (Other languages may use more than one. The letter characters are ordinary spacing characters, that are manually positioned in the text stream.)
2. Tone marks [4] (see tones) Tone marks should be typed and stored immediately after a dependent vowel, if there is one, and immediately after the base otherwise.
3. Consonant killer (májtʰantʰákʰâːt) [1] (see novowel) Used after other elements in the grapheme cluster to indicate cancelling of a consonant or syllable.

The spacing letters used for vowel signs are all individual grapheme clusters, with the exception of ำ (see nikhahit), which has the general category of Letter, but it is treated like a combining mark during segmentation.

The following examples show a variety of grapheme clusters:

Click on the text version of these words to see more detail about the composition.

	ได้กลิ่น
	ห้องน้ำ
	โปรแกรม
	ศักดิ์สิทธิ์

The grapheme cluster boundaries are convenient for justification algorithms, which insert equal amounts of space between non-combining letters, including between non-combining vowel sign components and their consonants (see justification).

One exception is the aforementioned ำ, which is split across 2 typographic units for the purpose of justification (see inter_character_spacing).

Phrase & section boundaries

Thai uses space as a phrase marker, rather than to delimit words, often in places where English text would use commas or periods. Latin-based punctuation such as comma, period, and colon are also used in text, particularly in conjunction with Latin letters or in formatting numbers, addresses, and so forth.

๚ is used to mark the end of a long segment of text. It can be combined as follows to mark a larger segment of text; typically this usage can be seen at the end of a verse in poetry.u,625

๚ะ

๛ marks the end of a chapter or document, where it always follows the ๚ะ combination.u,625

Dashes include

Space widths

It is possible to find two different sizes of space in Thai: large spaces between sentences, and small spaces in other places (eg. for separating sub clauses). The width of the small space is the same as ก, and the larger space is double that size.@GitHub,https://github.com/w3c/sealreq/issues/46

Most people no longer make this distinction, but some may want to. It also occurs in other Southeast Asian scripts.

Observation: It is currently not clear how to achieve this on the Web, where multiple space characters are collapsed to a single space by default. One suggestion is to use   [U+2003 EM SPACE], but that is not well supported by Thai fonts, and doesn't expand during justification. See @GitHub,https://github.com/w3c/sealreq/issues/46 for a discussion.

Quotations & citations

Thai texts use quotation marks around quotations. Of course, due to keyboard design, quotations may also be surrounded by ASCII double and single quote marks.

Abbreviation, ellipsis & repetition

Other inline features

Line breaking & hyphenation

Even where Thai doesn't indicate word boundaries, when Thai text is wrapped at the end of a line it should break at word boundaries.

As the width of a browser window changes, the text in fig_thai_wrap should break at the points shown if the browser supports Thai wrapping:

Because Thai doesn't separate words, applications typically look up word boundaries in a dictionary, however, such lookup doesn't always produce the needed result, especially when dealing with compound words and proper names (see #word). For more details, see wordBoundary.

To counteract these deficiencies, authors may use 200B and 2060 (see zwsp).

Note that most browsers have heuristics for segmenting Thai text, but there is no guarantee that these rules will work equally well for other languages that are written in the Thai script.

Text alignment & justification

Justification in Thai primarily adjusts the blank spaces between phrases, rather than expanding the text between words or syllables. The fact that lines break at word boundaries helps reduce the size of the gaps produced.

Thai may also make certain adjustments to inter-character spacing. The character-based spacing is most common in narrow columns, such as newsprint, where there is no space except at the end of a line.

Any 200B (ZWSP) is used to separate words is ignored during justification. Justification proceeds as if it wasn't there.u,625

Inter-character spacing

The justification in fig_justification_intercharacter_spacing shows equal spacing across a phrase where there are no space characters to stretch. Note how the equal spacing separates pre-base and post-base vowel sign components from their consonants by the same amount as consonants are separated from each other; they are not kept together with the base consonant they modify.

This kind of spacing requires a special behaviour for ำ. The small circle is kept with the preceding consonant, and space is added before the spacing part of the vowel, as shown in fig_am_spacing.

(To facilitate this, applications tend to convert ำ to the sequence ํา before stretching. Some care has to also be taken to correctly order the superscript glyphs, since in memory the tone mark precedes the nikhahit. The nikhahit character is not otherwise used for modern Thai.)

Paragraph indentation

Thai does indent the initial line of a paragraph.

Baselines, line height, etc.

Thai uses the so-called 'alphabetic' baseline, which is the same as for Latin and many other scripts.

Thai places vowel and tone marks above base characters, one above the other, and can also add combining characters below the line. The complexity of these marks means that the vertical resolution needed for clearly readable Thai text is higher than for English, or most Latin text. In addition, Thai tends to adds more interline spacing than Latin text does.

To give an approximate idea, fig_baselines compares Latin and Thai glyphs from Noto fonts. The basic height of Thai letters is typically around the Latin x-height, however extenders and combining marks reach well beyond the Latin ascenders and descenders, creating a need for larger line spacing. In other fonts, the basic height of the Thai letters tends to be between the Latin x-height and cap-height, and the overall height of the Thai line is therefore greater.@GitHub,https://github.com/w3c/sealreq/issues/55#issuecomment-1356183447 See for example the Angsana New and FreesiaUPC font samples below.

fig_baselines_other shows similar comparisons for the Thonburi and Angsana New fonts.

Counters, lists, etc.

You can experiment with counter styles using the Counter styles converter. Patterns for using these styles in CSS can be found in Ready-made Counter Styles, and we use the names of those patterns here to refer to the various styles.

The modern Thai orthography uses numeric and alphabetic styles.

Examples:

Styling initials

It is possible to find the first letter in a paragraph styled so that it is larger and sits alongside several lines of the continuing paragraph text.

Observation: All combining characters are included in the selections shown in fig_drop_caps.

Any punctuation such as opening quotes and opening parentheses should also be included in the initial styling. ?

Observation: In the figures shown, the alphabetic baseline of the highlighted letter falls slightly below the bottom of the row that determines the size of the highlighted letter. It's not clear whether that's a general trend, or just related to this specific publication.

Observation: In fig_drop_caps_2, the selection picks out only แ from the syllable แฉ.