Hill tribe is a term used in Thailand for all of the various tribal peoples who migrated from Yunnan, Tibet, or elsewhere in China over the past few centuries. They now inhabit the remote border areas between Northern Thailand, Laos and Burma (Myanmar). These areas are known for their thick forests and mountainous terrain. The six major hill tribes within Thailand are the Akha, Lahu, Karen, Hmong/Miao, Mien/Yao and Lisu, each with a distinct language and culture.
The hill tribes are subsistence farmers who use slash and burn agricultural techniques to farm their heavily forested communities. Tighter conservation of Thailand’s virtually depleted forests, however, has forced hill tribe people to abandon their traditional agricultural methods. Traditionally, hill tribes were also a migratory people, leaving land as it became depleted of natural resources.
Quoted from Wikipedia