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.
Mae Hong Son Province Moei, ). Most of the areas of Mae Hong Son Province are the complex mountain ranges of the Thai highlands, parts of which are still covered with rain forest. Of the approximately 6,976,650 rai of national forest reserves, it is estimated that 88 percent is pristine virgin forest. The Daen Lao Range, in the northernmost portion of the province, marks the northern boundary between Thailand and Burma, while the Dawna Range in the west serves as the boundary between Thailand and Burma. The Thanon Thongchai Range in the east of the province serves as the boundary between the provinces of