The Thai alphabet uses forty-four consonants and fifteen basic vowel characters. These are horizontally placed, left to right, with no intervening space, to form syllables, words, and sentences. Vowels are written above, below, before, or after the consonant they modify, although the consonant always sounds first when the syllable is spoken. The vowel characters (and a few consonants) can be combined in various ways to produce numerous compound vowels (diphthongs and triphthongs). Unlike the Chinese language, Thai is alphabetic, so pronunciation of a word is independent of its meaning . On the other hand, Thai is tonal, like Chinese and unlike English. This means that each word has a certain pitch characteristic with which it must be spoken to be properly understood. The Thai language uses five tones: mid, low, high, rising, and falling. Each syllable, consisting of one or more consonants and a simple or compound vowel has a default tone determined by several factors, including the type of consonant(s) present (consonants are divided into three classes for this purpose). The syllable's tone can be modified by one of four tone marks. The final tone of a syllable is determined by the tone mark in conjunction with the type of syllable, as determined by the vowel and consonant characters present.

Linguistics is the scientific study of language. Someone who engages in this study is called a linguist. Contemporary linguists work under the assumption that spoken language is more fundamental, and thus more important to study, than written language. Theoretical linguistics encompasses a number of sub-fields, such as the study of language structure (grammar) and meaning (semantics). The study of grammar encompasses morphology (formation and alteration of words) and syntax (the rules that determine the way words combine into phrases and sentences). Also part of this field are phonology, the study of sound systems and abstract sound units, and phonetics, which is concerned with the actual properties of speech sounds (phones), non-speech sounds, and how they are produced and perceived. Linguistics compares languages (comparative linguistics) and explores their histories to find universal properties of language and to account for its development and origins (historical linguistics). Applied linguistics puts linguistic theories into practice in areas such as foreign language teaching, speech therapy, translation, and speech pathology.