ThaiPronunciation: /tʌɪ/Translate Thai | into German | into Italian | into Spanish Definition of Thai adjective relating to Thailand, its people, or their language. noun (plural same or Thais) 1a native or inhabitant of Thailand. a member of the largest ethnic group in Thailand. a person of Thai descent. 2 [mass noun] the official language of Thailand, spoken by over 20 million people, mainly in central Thailand. It belongs to the Tai language group. Origin:Thai, literally 'free'Thai in other Oxford dictionaries Definition of Thai in the US English dictionary