Si Thep is known as one of the large ancient cities which are located on the Pa Sak River in Phetchabun Province. The city had been developed since the time of the bronze-iron age about 2,000 years ago.
Around the 11th -12th century B.E., Si Thep was ruled by a king and dominated by Hinduism beliefs. From the 13th century B.E. onwards, Buddhism of both Hinayana and Mahayana sects were prevalent here.
In the 16th to 17th century. During that time, the Lop Buri Kingdom began a new relationship with the Khmer Empire and adopted Hinduism beliefs as the main religion.
Si Thep was completely abandoned in the 18th century B.E. and turned into a small town on a communication route between the central plain of the Chao Phraya river basin and the central plain of Khorat.