The Tham Heup is a large and impressive cave that you can walk right through. The cave is 1.1km long, and has some beautiful rock formations, a pond, and a beach. The entrance is 20m wide and 15m high, with a interior that varies from 10m to 30m high.
The cave can be accessed from Ban Nakhok village by crossing the Hinboun River and walking for 1.5km. In the wet season the cave can be reached by boat along a branch of the Hinboun River near Ban Nakhok. About 3-4km south-east of the cave is a beautiful sacred forest with an abandoned temple. Also in the area is a small Buddha cave called Tham Jong. A local guide is required for these visits and can be arranged in Ban Nakhok.