Rock formations are what Pa Hin Ngam are known for, and what the name actually means. While I definitely enjoyed the Siam tulip fields a lot more, these rock formations are really cool and interesting. Erosion has worn the rocks down into different and interesting shapes. A small path winds through the field of rocks so you can see each one. There are some quite stunning views. I did manage to get a little turned around even though you can see the exit, the path is not always easy to find. That made it a little more interesting. =)
Sadly, many of the rock formations are being damaged from people climbing on and around them. They are not just getting worn smooth, they are getting chipped away. The rock is fragile, which is why it has been able to erode away into these formations in the first place. The area around the rocks is also covered in garbage which seriously detracts from the appeal.
Few foreigners visit Pa Hin Ngam National Park. It is mostly just Thai people. The park is not that difficult to get to from Bangkok, though it does take some time. Minibuses do run to the park and there are small hotels around it. There is not much here except the park itself, and you can see the rock formations and the Siam tulips fields in one day easily, but if you have the time and want to make the effort I think it is worth it.