When used as an adjective, Thai refers to anything that originates from Thailand. As a noun it may refer to more than one article:

Thai alphabet, the writing system of Thai and other minority languages in Thailand

Thai food, the cuisine of Thailand

Thai language, a Tai-Kadai language spoken mainly in and around Thailand

Thai people, the dominant ethnic group of Thailand

Thai culture

Thai Airways International, the national airline of Thailand

Thai, a month in the Tamil calendar

Thai tea or "cha-yen", a drink made from black tea

Thai Ngo, an Asian American rapper

Thai, slang for cannabis mixed with tobacco, commonly smoked in a bong. Thai is also a strain of cannabis.