River systems of Thailand divides into two major branches, the " Tiền Giang" (Front River) and "Hậu Giang" (Back River). These in turn enter the South China Sea through nine estuaries. The following are the principal tributaries of Mekong River which flow through Thailand (tributaries entirely outside the Thai border not shown). The Mekong drains a considerable portion of northeast Thailand. In terms of Thai territory drained, it is second only to the Chao Phraya system. The Salawin River rises in Tibet (Tibetan: རྒྱལ་མོ་རྔུལ་ཆུ།) after which it flows through Yunnan, where it is known as the "Nujiang" River (), although either name can be
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