Chainat is one of the central provinces of Thailand. Neighboring provinces (from north clockwise) Nakhon Sawan, Sing Buri, Suphan Buri and Uthai Thani. Tea Nat is in a flat river plain of central Thailand's Chao Phraya River valley. In the southern province of Chao Phraya (formerly Tea NAT) impounds a dam on the river Chao Phraya, how to deal with floods, as well as to divert water in the country's largest irrigation system to irrigate rice fields at the bottom of the river valley.

Originally Chainat was located on Sankhaburi. In the reign of king Mongkut (Rama IV) the main settlement in the province was moved to its present location. During the wars with the Burmese, it is an important military base to confront with the Burmese arms. As all these confrontations were successful the city was named Tea NAT, which means place of victory. The provincial seal shows the Buddhist wheel, Dhammajakra. In the background the mountain (Khao Phlong) and river (Chao Phraya River). The wheel symbolizes the faith of the people.