Who they were
Mangrai was born in 1238 into the ruling line of Ngoenyang (Chiang Saen) and succeeded to its throne in 1259. He died around 1311.
What they did
Mangrai unified the northern Tai mueang. He founded Chiang Rai in 1262, naming it for himself, and conquered the Mon kingdom of Hariphunchai (Lamphun) in the 1280s–90s (chronicle datings vary). In 1296 he founded Chiang Mai — the “new city” — as his capital. By northern tradition, he sealed a friendship pact with Ram Khamhaeng of Sukhothai and Ngam Mueang of Phayao, an alliance commemorated by Chiang Mai’s Three Kings Monument. A customary law code, the Mangraisat, is attributed to him by tradition.
Legacy
Northern chronicles say Mangrai was struck by lightning in a Chiang Mai market around 1311 — a chronicle account. His dynasty ruled Lan Na for some two centuries, and he remains a foundational figure of northern Thai identity.