Thailand, Gulf of, or Gulf of Siam, shallow arm of the South China Sea, c.500 mi (800 km) long and up to 350 mi (560 km) wide, separating the Malay Peninsula from E Thailand, Cambodia, and S Vietnam. Bangkok, the gulf's chief port, is at the mouth of the Chao Phraya River.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.