River systems of Thailand used for the whole river. The river is long. It then leaves China and meanders through Myanmar (where it is known as the "Thanlwin") and Thailand (where it is known as the "Salawin", Thai: สาละวิน) on its way to emptying into the Andaman Sea by Mawlamyaing (Moulmien). The principal tributaries of the Salawin which flow through Thailand are the Moei River and the Pai River. In addition to the Salween River, there are a number of rivers which drain into the Andaman Sea from the west coast of the Malay Peninsula. None of them are extensive enough to be considered
Salween River National Park to join the Moei River from the east as it approaches Thailand, where it is called the "Salawin", forming the Burma-Thailand boundary for about , before re-entering Burma, passing through Karen State and Mon State. The river finally breaks out of its gorge about from the mouth, and slows down dramatically as it courses through a series of agricultural valleys. About from the mouth the river finally widens and deepens enough to become navigable for large watercraft. In quick succession it receives Dontham River from the right and Gyaing River from the left, from where the river turns