The Golden Triangle is one of Asia's two main illicit opium-producing areas. It is an area of around 350,000 square kilometres that overlaps the mountains of four countries of Southeast Asia: Myanmar (Burma), Vietnam, Laos, and Thailand. (Other interpretations of the Golden Triangle also include a section of Yunnan Province, China.) Along with Afghanistan in the Golden Crescent and Pakistan, it has been one of the most extensive opium-producing areas of Asia and of the world since the 1950s. The Golden Triangle also designates the confluence of the Ruak River and the Mekong river, since the term has been appropriated by the Thai tourist industry to describe the nearby junction of Thailand, Laos, and Burma.

http://en.wikipedia.org/wiki/Golden_Triangle_(Southeast_Asia...