Chiang Rai is one of Thailand's seventy-six provinces, which lies in upper northern Thailand and is Thailand's northernmost province. It is bordered by the Shan State of Myanmar to the north, Bokeo province of Laos to the east, Phayao to the south, Lampang to the southwest, and Chiang Mai to the west. The provinces is linked to Houayxay Laos by the Fourth Thai–Lao Friendship Bridge that spans the Mekong.

The Golden Triangle is a large, mountainous region of approximately 200,000 km2 (77,000 sq mi) in northeastern Myanmar, northwestern Thailand and northern Laos, centered on the confluence of the Ruak and Mekong rivers. The name "Golden Triangle" was coined by Marshall Green, a U.S. State Department official, in 1971 in a press conference on the opium trade. Today, the Thai side of the river confluence, Sop Ruak, has become a tourist attraction, with an Opium Museum, a Hall of Opium, and a Golden Triangle Park, and no opium cultivation.