Through the town of Chiang Rai itself, flows the 'Mae Kok' Kok Riverand south of it the Lao River, a tributary of the Kok.While the eastern part of the province is characterized by relatively flat river plains, the northern and western part consist of the hilly terrain of the Hills of Northern Thailandwith the Khun Tan Range and the Phi Pan Nam Range in the west and the Daen Lao Range in the north. While not