نهر تشاو فرايا
The expanse of the Chao Phraya River and its tributaries, i.e., the Chao Phraya river system, together with the land upon which falling rain drains into these bodies of water, form the Chao Phraya watershed. The Chao Phraya watershed is the largest in Thailand, covering approximately 35 percent of the nation's area, and draining an area of .