The city was founded by King Mangrai in 1262 and became the capital of the Mangrai dynasty. Subsequently, Chiang Rai was conquered by Burma and remained under Burmese rule for several hundred years. It was not until 1786 that Chiang Rai became a Chiang Mai vassal. Siam (Thailand) annexed Chiang Mai in 1899, and Chiang Rai was proclaimed a province of Thailand in 1933.
Chiang Rai City lies in the flat alluvial plain of the Mae Kok River, a tributary of the Mekong, between the Daen Lao Range in the north and the Phi Pan Nam Range in the south. The Mae Kok River runs along Chiang Rai's north side, flowing eastwards out of Burma at Taton town, bending northeastwards and joining the Mekong River about 40 km northeast of the city. The Lao River, a tributary of the Kok, flows south of Chiang Rai.
There are four bridges spanning the Mae Kok river within the town's boundaries, each running south/north. Most of the terrain surrounding Chiang Rai town is either flat or has moderate hills. The exception is outward in the west and northwest directions, where limestone hills are evident, some of which have straight-up exposed cliffs. Not surprisingly, that is also the direction where most of the region's Hill Tribe people have their villages, further afield.
The city is located 860 km north of Bangkok, about 200 kilometres northeast of Chiang Mai City, 62 kilometres south of Mae Sai and the Burmese border; 60 kilometres southwest of the town of Chiang Saen on the Mekong River across from Laos; and 90 kilometres north of Phayao town. The Golden Triangle, the tripoint of the Thailand, Laos and Myanmar borders, is 55 km northeast of the city.