U Thong is the district (amphoe) in the western part of Suphanburi Province, north of Bangkok. U Thong was occupied for many centuries prior to the development of the Dvaravati state. Radiocarbon determinations from the sites of U Thong and Chansen suggest that the transition into complex state societies in the Chao Phraya basin took place between about 300-600 AD. Important in the Dvaravati Era, U Thong would go on to witness the the birth of the new kingdom of Ayutthaya, it's first king taking on the name Uthong.