There are a number of wonderful caves which can be visited in Chumphon Province.
There are a number of different tour companies operating now, so ask around at a couple different place to plan the kind of expedition that's right for you. Some of the caves are an easy visit, but others attract hard-core spelunkers with challenging climbs involving ropes and other caving equipment. One day tours start at about 700 THB per person, depending on the size of the group, but longer tours can be arranged, and if you find a new cave you get to name it!! (We think Tham Travelfish has a nice ring to it, but that's just a suggestion.) These tours are generally for small groups of two to four only.
Situated by Wat Thap Charoen (also known as Wat Rubror) is a series of interesting caves including Tham Phra which is the largest and contains a multitude of Buddha images. The biggest and oldest statue is a 6m high stone Buddha which is rumoured to be over 1,000 years old. Nearby Tham Ai Teh is reputed to have been the scene of human sacrifices at one time and it is also thought by locals to contain a hidden treasure map indicating the location of a nearby hoard. This treasure consists of the plentiful offerings made by various wealthy pilgrims to the venerable Buddha image in Tham Phra. Please do not start digging up the cave though as it is a National Heritage Site and the map will be in Thai anyway!
In the same cave system are also Tham Phet (Diamond Cave) and Tham Chang (Elephant Cave). Several of the caves had electricity installed by the monks so a donation is always appreciated.
To reach Tham Rubror head out of Chumphon west onto the main north-south highway. From here north for 9km until you see the sign on the left, then follow the track for 5km to Wat Rubror. Local buses ply the highway and there are usually motorbike taxis at the junction that will take you the remaining 5km to the cave for around 20B.
The entrance to this cave is far more impressive than the small interior, but if you only have time for one cave, it's easy to reach and we found a nice back road you can take to reach it. If you have a bicycle or motorcycle, head left from the train station on the road along the track until it dead ends at the over pass. Go left on to Muang Chumphon, take the first u-turn, and take the exit road just before the overpass. Turn left on Muang Chumphon Soi 13 (Wat Haadsakiew) and you'll immediately leave the city behind and find yourself winding your way to through the country side. When you reach Petchakassem Rd. 8 km later, go left and take the first u-turn. Back track until you see a large restaurant on your left and turn left. You'll proceed down this road until it bears left and turns to dirt. Turn right at the end of the dirt road and the Wat is on the left. Don't be shy about asking around along the way if you're confused--the locals all know the way. If you arrive in the middle of the day, the nuns might even feed you.
Continuing up the same highway, 15km from the junction with the main road, is the English signposted turn-off to Pee-Sa-Dan Cave. A dirt track 3km long takes you to Wat Pee Sa Dan where, as usual, the local monks have conveniently strung a few light bulbs around the spectacular Tham Pee-Sa-Dan (the English translation of which is 'Strange Cave'). It is not particularly strange, but does have some great stalagmites and stalactites.
The above two caves can easily be visited under your own steam, but there are many other caves in this area, which are best visited on an organised trip. Ask at any of the travel agencies in town.