Thai phonology

## Consonants

### Initials

Standard Thai distinguishes three voice-onset times among plosive and affricate consonants:

* voiced
* tenuis (unvoiced, unaspirated)
* aspirated

Where English makes a distinction between voiced /b/ and unvoiced aspirated /pʰ/, Thai distinguishes a third sound - the unvoiced, unaspirated /p/ that occurs in English only as an allophone of /pʰ/, for example after an /s/ as in the sound of the *p* in "spin". There is similarly an alveolar /d/, /t/, /tʰ/ triplet in Thai. In the velar series there is a /k/, /kʰ/ pair and in the postalveolar series a /t͡ɕ/, /t͡ɕʰ/ pair, but the language lacks the corresponding voiced sounds /ɡ/ and /dʑ/. (In loanwords from English, English /ɡ/ and /d͡ʒ/ are borrowed as the tenuis stops /k/ and /t͡ɕ/.)

In each cell below, the first line indicates International Phonetic Alphabet (IPA), the second indicates the Thai characters in initial position (several letters appearing in the same box have identical pronunciation). The letter ห, one of the two *h* letters, is also used to help write certain tones (described below).

### Finals

Although the overall 44 Thai consonant letters provide 21 sounds in case of initials, the case for finals is different. For finals, only eight sounds, as well as no sound, called *mātrā* (มาตรา) are used. To demonstrate, at the end of a syllable, บ (/b/) and ด (/d/) are devoiced, becoming pronounced as /p/ and /t/ respectively. Additionally, all plosive sounds are unreleased. Hence, final /p/, /t/, and /k/ sounds are pronounced as [p̚], [t̚], and [k̚] respectively.

Of the consonant letters, excluding the disused ฃ and ฅ, six (ฉ ผ ฝ ห อ ฮ) cannot be used as a final and the other 36 are grouped as following.

### Clusters

In Thai, each syllable in a word is considered separate from the others, so combinations of consonants from adjacent syllables are never recognised as a cluster. Thai has phonotactical constraints that define permissible syllable structure, consonant clusters, and vowel sequences. Original Thai vocabulary introduces only 11 combined consonantal patterns:

* /kr/ (กร), /kl/ (กล), /kw/ (กว)
* /kʰr/ (ขร,คร), /kʰl/ (ขล,คล), /kʰw/ (ขว,คว)
* /pr/ (ปร), /pl/ (ปล)
* /pʰr/ (พร), /pʰl/ (ผล,พล)
* /tr/ (ตร)

The number of clusters increases when a few more combinations are presented in loanwords such as /tʰr/ (ทร) in อินทรา (/intʰraː/, from Sanskrit *indrā*) or /fr/ (ฟร) in ฟรี (/friː/, from English *free*); however, it can be observed that Thai language supports only those in initial position, with either /r/, /l/, or /w/ as the second consonant sound and not more than two sounds at a time.

## Vowels

The vowel nuclei of the Thai language are given in the following table. The top entry in every cell is the symbol from the International Phonetic Alphabet, the second entry gives the spelling in the Thai alphabet, where a dash (–) indicates the position of the initial consonant after which the vowel is pronounced. A second dash indicates that a final consonant must follow.

 High | /i/ -ิ
 Mid | /e/เ-ะ
 Low | /ɛ/แ-ะ

The vowels each exist in long-short pairs: these are distinct phonemes forming unrelated words in Thai, but usually transliterated the same: เขา (*khao*) means "he" or "she", while ขาว (*khao*) means "white".

There are also opening and closing diphthongs in Thai, which analyze as underlyingly /Vj/ and /Vw/. For purposes of determining tone, those marked with an asterisk are sometimes classified as long:

Additionally, there are three triphthongs. For purposes of determining tone, those marked with an asterisk are sometimes classified as long:

## Tones

There are five phonemic tones: mid, low, falling, high, and rising, sometimes referred to in older reference works as *rectus, gravis, circumflexus, altus,* and *demissus,* respectively. The table shows an example of both the phonemic tones and their phonetic realization, in the IPA.

Notes:

1. Five-level tone value: Mid [33], Low [21], Falling [43], High [44], Rising [323]. Traditionally, the high tone was recorded as either [44] or [45]. This remains true for the older generation, but the high tone is changing to [334] among youngsters.
2. For the diachronic changes of tone value, please see Pittayaporn (2007).
3. The full complement of tones exists only in so-called "live syllables", those that end in a long vowel or a sonorant (/m/, /n/, /ŋ/, /j/, /w/).
4. For "dead syllables", those that end in a plosive (/p/, /t/, /k/) or in a short vowel, only three tonal distinctions are possible: low, high, and falling. Because syllables analyzed as ending in a short vowel may have a final glottal stop (especially in slower speech), all "dead syllables" are phonetically checked, and have the reduced tonal inventory characteristic of checked syllables.

### Checked syllables

In some English loanwords, closed syllables with long vowel ending in an obstruent sound, have high tone, and closed syllables with short vowel ending in an obstruent sound have falling tone.

1 May be /báːs.kêt.bɔ̄l/ in educated speech.

## References

1. ↑ Frankfurter, Oscar. Elements of Siamese grammar with appendices. American Presbyterian mission press, 1900 [1] (Full text available on Google Books)
2. ↑ Teeranon, Phanintra. (2007). "The change of Standard Thai high tone: An acoustic study and a perceptual experiment". *SKASE Journal of Theoretical Linguistics, 4*(3), 1-16.
3. ↑ Thepboriruk, Kanjana. (2010). "Bangkok Thai Tones Revisited". *Journal of the Southeast Asian Linguistics Society, 3*(1), 86-105.
4. ↑ Pittayaporn, Pittayawat. (2007). "Directionality of Tone Change". *Proceedings of the 16th International Congress of Phonetic Sciences (ICPhS XVI)*.