Chiang Rai is the most northern province of Thailand. Neighboring provinces (from east clockwise) Phayao, Lampang and Chiang Mai. In the north it borders Shan State of Myanmar and Bokeo Udomsay and Laos. The average height of the province was 580 M. At the north edge of belongs to the so-called "Golden Triangle", which borders Thailand, Laos and Myanmar converge - an area which is very unsafe because of drug smuggling across the border. On the Mekong River forms the border with Laos, the Mae Sai and Ruak River in Myanmar. In the city of Chiang Rai is derived River Kok.

While in the eastern province of a relatively flat river plains, the western part consists of mountainous terrain in the mountains of Northern Thailand. Although not high in the province, at 1389 m. At Wat Phra That Doi Tung temple on top of the hill according to the chronicle refers to the year 911. Nearby is the Doi Tung royal villa, former residence of the late Princess Mother (mother of current King) Somdej Phra Srinagarindra. Through its activities were wooded hills and the hill tribes changed from growing poppies to other crops.