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
Sai River (Thailand) flowing through the Tachileik/Mae Sai urban area, where there is a sign marking the northern most point of Thailand just east of the border-crossing bridge —at the meeting point of Thailand Route 1 and National Highway 4 (Burma)— over the river. Finally it flows northeastwards before joining the right side of the Ruak River, a tributary of the Mekong, less than southeast of Tachileik Airport. Sai River (Thailand) Sai River (; ; ), formerly known as the River of Lawa (; ), is a river that forms the natural border between Thailand and Myanmar at Tachileik and Mae Sai Districts.