My rating:
Although the city of Lopburi is generally considered the western frontier of the old Khmer empire, the cultural influence of Angkor extended much further, and Wat Kampaeng Laeng is evidence of that. As Khmer ruins go, the 700 year old temple is not very impressive, but it's probably still worth a stop when touring Petchburi.
The ruins of Wat Kampaeng Laeng
The ruins comprise four stone structures that were once covered in fine stucco decorations, all of which has worn away over time. The English information sign is almost complete gibberish, so there isn't much to guide you through the complex. It probably was originally a Hindu temple, owing to the three main shrines. The eastern-most structure was probably a gateway (gopura) which would have allowed access to the inner sanctuary. A wall probably surrounded the other three towers, but either it was made of wood that has rotted away or the stones were carried off for other purposes.
The three towers are mostly intact, although the middle one is missing its top. At some point, the temple was converted to Buddhist worship, and there is now a large, modern Buddhist temple compound next to the ruins.
There is no admission fee to visit the ruins.