Khao Klang Nai Archaeological Site is located in the inner city of Si Thep and is a Buddhist religious place since the early days of the city establishment around the 12th Buddhist century. At the first stage of the excavation, it was found that this archaeological site was built according to Theravada Buddhism in the respect of the first Dvaravati culture. Later in the 14th century, the sect was changed into Mahayana Buddhism as many sculptures of Bodhisattva were found and there are signs of repairs in the same period, along with the stucco decoration on the base of the building, which still remains on the west and south.