The Thai writing system was devised to serve two main purposes: to write Thai words and to write Sanskrit (or Pali) words. For this reason, the Thai alphabet has one consonant symbol for each Sanskrit sound and several additional consonant symbols which, presumably, corresponded to Thai sounds which did not occur in Sanskrit.

The Thai consonant symbols which corresponded to Sanskrit consonant sounds were as follows:

ก (k), ข (kh), ค (g), ฆ(gh), ง (ng),

จ (c), ฉ (ch), ช (j), ฌ (jh), ญ (ny),

ฏ (T), ฐ (TH), ฑ (D), ฒ (DH), ณ (N),

ต (t), ถ (th), ท (d), ธ (dh), น (n),

ป (p), ผ (ph), พ (b), ภ (bh), ม (m),

ย (y), ร (r), ล (l), ว (w),

ศ (sh), ษ (S), ส (s), ห (h), ฬ (L),

The remaining consonant symbols in the Thai alphabet are as follows:

ฃ, ฅ, ซ, ฎ, ด, บ, ฝ, ฟ, อ, ฮ.

These remaining symbols presumably corresponded to consonant sounds which existed in the Thai language but not in Sanskrit. My best guesses for these sounds (based on what I have read as well as the position in the alphabet where these symbols occur) is as follows:

ฃ, like ch, as in Scottish loch,

ฅ, like r, as in French rouge,

ซ, like s, as in English measure,

ฎ, possibly a glottal stop followed by a retroflex T or D,

ด, a glottal stop followed by a t or d,

บ, a glottal stop followed by a p or b,

ฝ, like f, as in English fan,

ฟ, like v, as in English van,

อ, (when used as a consonant) is (and probably always was) a glottal stop,

ฮ, I think this letter was added to the alphabet later, sounding like the existing letter ห (h), but producing different tones.

I guess that all of the symbols which corresponded to Sanskrit sounds would have originally made the same sound whenever that sound actually occurred in the spoken Thai language. So for example, I guess (from what I have read) that the Thai letters ค, ช, ท and พ were originally pronounced as the unaspirated, voiced Sanskrit sounds g, j, d and b (although they are now pronounced like the aspirated, unvoiced Sanskrit sounds kh, ch, th and ph).

I have several questions:

  1. Is it known whether the spoken Thai language(s) ever used the voiced, aspirated Sanskrit consonant sounds gh, jh, dh, bh (which do not occur in modern Thai, or in English)?

  2. Is it known whether the spoken Thai language(s) ever used the retroflex Sanskrit consonants T, TH, D, DH, N (which do not occur in modern Thai, or in English)? My only (somewhat feeble) reason for guessing that these sounds may have occurred is the existence of the Thai consonant symbol ฎ, which may have represented a glottal stop followed by a retroflex T or D. If these retroflex sounds did not occur in Thai then what was the sound produced by the consonant symbol ฎ?

  3. Are any of my above guesses, as to the original pronunciations of the symbols ฃ, ฅ, ซ, ฎ, ด, บ, ฝ, ฟ, อ, ฮ (which do not correspond to Sanskrit consonants), known either to be true or to be false?

Finally, if the answers to some of my questions are known, or at least if there are some conjectures as to the answers, then what is the basis on which the conjectures are founded? That is, what is the evidence that might lead one to make more educated guesses than I myself have made (I am only hoping for a brief answer here)?

  • The articles linked to in Michaelyus's answer at linguistics.stackexchange.com/questions/34824/… may be helpful. Lanna may give you a clue as to ฃ and ฅ, as at least some people maintain that the Tai Tham equivalents are not obsolete, i.e. that they still differ from the equivalents of ข and ค.
    – rchivers
    Jan 9, 2021 at 5:45
  • Thanks. I was not able to look at those linked articles (browser problems?), but I have been browsing through some other scholarly articles (which I find difficult to read, not being a linguist).
    – snew
    Jan 9, 2021 at 17:39
  • Maybe it depends where your IP is. The position of ซ has always puzzled me. It's clear that it's needed in modern Thai to provide a low class /s/, but if that was its original function, why insert it where it is? If you theorize that the pronunciation of ส etc was closer to modern จ, it makes sense that the low class equivalent would be based it on ช and (therefore) inserted after ช. Otherwise it's a mystery, at least to me. It might be relevant to find out whether Lao ຊິ (=ซิ) and ຈະ come from the same root.
    – rchivers
    Jan 10, 2021 at 3:14
  • A wiki talk page (en.wikipedia.org/w/…) says "HIGH KXA (ᨢ) ฃ isn't totally obsolete. The Maefahluang Northern Thai-Thai dictionary uses it for primary entries of words. The reason for creating it from HIGH KHA (ᨡ) still existed in Cheng Tung ... The most recent confirmation I can find is noted in A Sociolinguistic Survey of Lue in Mong Yawng. It seems that the speakers thought of themselves as Tai Lue, but actually spoke White Tai, where the difference lives on." It doesn't say exactly what the difference is though.
    – rchivers
    Jan 10, 2021 at 3:17
  • I do not think it is likely that ซ was added to serve its modern purpose of producing the the same s sound as ส, but with a different tone. I am guessing that it was used to produce a different sound. The Lao script was more or less obtained from the old Thai script by dropping redundant consonant symbols. The Lao symbol ຂ (pronounced kh) looks like the old Thai symbol for ข. The Lao symbol ຊ (pronounced s) appears in words where the Thai language uses ช (pronopunced ch) and it does have a vague resemblance to the old Thai symbol for ช (but to be honest, it looks more like ຂ).@rchivers
    – snew
    Jan 10, 2021 at 15:48

1 Answer 1


have you found any answers to question 2 (about ฎ)?

I was thinking about something similar but kind of doubt the existence of retroflex stops in (Old) Thai, because these phonemes do not seem to have existed in Proto Southwest Tai or any of the sister languages of Thai (Jonsson, 1991, pp. 52-53). Instead, I suppose that the symbol ฎ was created as a result of the merging of dental and retroflex consonants from Sanskrit or Pali loanwords into Thai. If this were not the case, we should be able to see ฎ appearing in original Thai words. But I cannot yet find any material discussing this (perhaps it's too obvious but I'm really not an expert on Thai). Please kindly let me know if you find any more information on this!

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