Phra Si Thep is the Khmer-architectural building facing west, built with bricks and laterite. The lotus-shaped lower base was made of laterite same as the Khmer general architecture while the principal building was built with bricks. According to the excavation of this area, the engraved lintel piece around the 16th-17th centuries was found. It is likely to be built for Khae Klang Nai Archeological Site, but later in the 18th century, there was an attempt to restore the building and not successful, some pieces of the construction were discovered in this area.