Thai language (tĪ) [key], formerly Siamese, member of the Tai or Thai subfamily of the Sino-Tibetan family of languages (see Sino-Tibetan languages). The official language of Thailand, Thai is spoken by approximately 50 million people in Thailand, Vietnam, and the Yunnan province of China. It has several dialects. Although most of the words are monosyllables, a number of them are polysyllabic. Because there is no inflection, word order is important for showing grammatical relationships. The Thai language is also tonal, and the tones serve to distinguish meanings of words otherwise pronounced alike. There are five tones: high, middle, low, rising, and falling. Over the centuries Thai has borrowed many words from Chinese, Khmer, Pali, Sanskrit, and, more recently, from European languages such as French and English. The Thai language has its own alphabet, which ultimately goes back to a script of S India and which was adopted in the 13th cent. A.D. Thai is written from left to right.
See E. M. Anthony et al., Foundations of Thai (1968); U. Warotamasikkhadit, Thai Syntax: An Outline (1972); M. R. Haas and H. R. Subhanka, Spoken Thai (1973).