Chiang Rai Northern border of Thailand. Chiang Rai was founded in 1262 by King Meng Rai and was the first capital of Lanna Thai (Kingdom of a Million Rice fields). The province contains Thailand's northernmost point at Mae Sai, which is well known for its crisp mountain scenery, and hill tribes. North of Chiang Rai is known as the Golden Triangle, the area where the borders of Thailand, Myanmar and Laos converge.