The Thai alphabet was developed by King Ramkhamhaeng the Great, of Sukhothai, in 1283. It was based on the ancient Indian alphabets of Sanskrit and Pali, which maintained their presence in South East Asia in the form of old Khmer characters.

The Thai alphabet today comprises 44 letters, representing 20 consonant phonemes, and 15 vowel signs, denoting 22 vowels, diphthongs and triphthongs. Consonants can take different sounds depending on whether they are at the beginning or end of a word. Vowels can stand before, after, above, or below the consonant that they support.

The "or" (open "o") vowel is never represented when no vowel is written. On the other hand, a short-duration "a" and "o" are the two possible default vowels represented when no vowel is actually written between consonants. (On the other hand, the "r" consonant represents the "or" vowel sound when it comes at the end of a word.) For example, consider the name of the Northeastern Thai province of Nakhon Phanom , meaning: "City by the Mountains." There are no written vowels in this four syllable word. 1- The unwritten vowel in the first syllable is "a" 2- The unwritten vowel in the second syllable is "or" (represented by the "r") 3- The unwritten vowel in the third syllable is "a" 4- The unwritten vowel in the forth syllable is "o" Another example is the word "person or people" . The unwritten in this word is "o"