We hired a car and drove out to the park. There is a 200 Baht per adult entrance fee. We almost drove past the entrance, as the park seems to have many entrances. One also gets an informative brochure of the park, including a map. Even with the map, and four intelligent people in the car, we almost lost our way. Upon entry, one has myriad sights to see. We decided on the Tham Phraya Nakon cave. We parked the car and were promptly informed that the only way to get there was by boat--at a price, of course. Fortunately, the brochure stated otherwise. Our hike began up and around a small hill--on a hot and humid day. It was a pebbly and rock-ridden hike up the hill, which wasn't a highlight, but the hike afforded a great view of the ocean and beach below. Our descent was rewarded with an almost deserted beach--white sand, lots of small conch-shaped shells, and bluey-green water.
We ventured further towards the cave, following the signs past camping huts. The path led further into a forested area, which got warmer and more humid. The climax of the hike was seeing notices of local monkeys that shouldn't be fed, i.e. don't brandish your candy bars, you may be relieved of it. This was also when the giant mosquitoes showed themselves. I say "giant" because one bite and you're scratching for days, and you'll end up with one rather large swollen spot. Plus, they were persistent--not easily brushed off, more like batted off.
A combination of fatigue, irritation, and dislike for bugs meant some of us ended up back on the beach, while others ventured on. The "steps" leading up to the cave were quite steep and far apart. The cave itself, I was told, was a sunken cave, with a temple of sorts inside.
The beach was pleasant enough and the walk back short. We drove back to the hotel afterwards. There are other things to see and do in the park, so don't dismiss it from my brief experience.