The consonants are divided according to their origin into three groups (not to be confused with the grouping for tone determination). From their use can be seen today only partly the origin of a word
a pure Thai word (if characters of group 3 are used)
Exception: ซ is often used for the transfer of English words
Loanword from Pali or Sanskrit (if characters of group 2 are used)
Loanword from Sanskrit (if one of the characters ศ or ษ are used)
This assignment is not definite. A word using the characters from the group 1 can be a pure Pali or Sanskrit word as well as one of other languages.
1. Neutral consonants
พยัญชนะกลาง[pha/yan--cha/na/gla:ng--]
The 21 consonants for the sounds that occur both in Thai and in the languages of Pali and Sanskrit as well as in the acquired Khmer, Mon, Java and English.
As the Thai pronunciation could be reproduced with the assumed characters only inadequate, it has developed the following additional 10 new characters:
Of the 10 newly added characters two are no longer used today. When the American McFarland beginning of the 20th Century created the first Thai typewriter through the conversion of an American unit, he was missing two buttons. He decided to omit the two characters kha:w khuat and kha:w khon (grey in the table above). Then, these two characters in modern Thai script was replaced by other K-sounds, and are missing since then.
With the consonants from Group 1 and 2 it was impossible to write Thai words as required by traditional pronouncing. There was, for example, Thai words that begin with "f", but no consonant sound like this. Or words with an "s" sound in a mid-level tone, could not be realized with the available consonants. Therefore the eight characters from the supplementary consonants which are still used today replace the pronunciation and spelling wherever it is necessary to correctly represent a Thai word.
This is a 'h' sound available even at the low consonants
Grouping of consonants according to their origin
The 44 consonants of the Thai script are predominantly from the languages Pali (Mon, South India) and Sanskrit (Khmer). Because Thai words could be transferred only inadequate with these consonants, some additional characters were developed.
