mountain pass in the Tenasserim Mountain Range on the Myanmar (Burma)-Thailand border, 100 miles (160 km) southeast of Moulmein, Myanmar. The pass, at an elevation of 925 feet (282 m), links southeastern Myanmar and western Thailand. For centuries it was the chief link between Myanmar and the fertile plain of the Chao Phraya River, used both for trade and for military invasions. During World War II the Japanese built the Thanbyuzayat–Ban Pong railroad (commemorated in the book and movie The Bridge on the River Kwai) through the pass (see Kanchanaburi).