Thai is the national and official language, though business people usually understand English and some Chinese dialects. Thai is the mother tongue of the Thai people, the country’s dominant ethnic group. Thai belongs to the Thai-Kadai language family, one of the five main language families in Southeast Asia.
It is a tonal language. It is generally agreed that the Thai alphabet was created from earlier regional scripts in 1283 by King Ramkhamhaeng the Great of the Sukhothai Kingdom.
Source: Thailand Executive Diary 2008