Salween River much of its length, the Salween's course is nearly parallel to that of the much larger Mekong in the east. Although the commonly accepted name is Salween, the river is known by a handful of other names regionally: "Nu" in China, "Thanlwin" in southern Burma, and "Salawin" on the border of Thailand and Burma. Several major sub-continental drainage basins border on the Salween. The Mekong basin forms nearly the entire eastern boundary of the watershed, while the Irrawaddy River flows southwards on the west side of the basin. The smallest boundary is formed by the Yangtze to the extreme north.
Peopling of Thailand through Laos. The Iu Mien arrived in Thailand approximately 200 years ago, contemporaneously with a large number of other Hmong–Mien migrants. The primary homeland of the Hmong–Mien ethnicity is said to be Kweichow, a province of southern China, where they settled at least 2,000 years ago. The Karen left Tibet and migrated to Burma as refugees, establishing themselves along the Burmese border with Thailand. When during World War II the Japanese occupied Burma, long-term tensions between the Karen and Burmese turned into open fighting. After the war ended, Burma was granted independence in January 1948, and the Karen, led by