Thai, Central Thai (historically Siamese; Thai: ภาษาไทย), is the sole official and national language of Thailand and the first language of the Central Thai people. It is a member of the Tai group of the Kra–Dai language family. Over half of Thai vocabulary is derived from or borrowed from Pali, Sanskrit, Mon and Old Khmer. It is a tonal and analytic language, similar to Chinese and Vietnamese.
Thai has a complex orthography and system of relational markers. Spoken Thai is mutually intelligible with Lao and Isan, fellow Southwestern Tai languages, to a significantly high degree where its speakers are able to effectively communicate each speaking their respective language. These languages are written with slightly different scripts but are linguistically similar and effectively form a dialect continuum.