Tônlé Sap, shallow lake, western Cambodia. The largest lake of Southeast Asia, it is fed by numerous streams; it drains by the Tônlé Sab River southeast to the Mekong River. During the wet monsoon season of June to November, the high waters of the Mekong River reverse the flow of the Tônlé Sab River and increase the size of the lake from 2600 to 10,400 sq km (about 1000 to 4,020 sq mi). Fishing is important on the lake.
ADDED: Microsoft Encarta 2004