Thai is a member of the Tai group of the Tai-Kadai language family. Historical linguists have been unable to definitively link the Tai-Kadai languages to any other language family. Some words in Thai are borrowed from Pali, Sanskrit and Old Khmer.
It is a tonal and analytic language. Thai also has a complex orthography and relational markers. Thai is mutually intelligible with Lao, whereas the Isaan dialect is almost the same.