Wat Phra Si Rattana Mahathat is the main attraction in the eastern section at Si Satchanalai Historical Park, Chaliang.
The temple compound likely was built in the 13th century with later additions during the Ayutthaya period. Khmer features at Wat Phra Si Rattana Mahathat indicate it was originally a Mahayana Buddhist site, dating to the reign of Jayavarman VII (1181-about 1219).
The main feature at the Wat is the impressive Ayutthaya-style prang, which appears to be a later addition. You will notice that the prang has a smooth contour leading to the top which is typical of Ayutthaya period prangs. Khmer-style prangs on the other hand are characterized by a step-like tapering towards the top.
While added later, the structure was probably built over an earlier one from the pre-Sukhothai period.