Khao Sok is a national park north of Phang Nga Bay, not far from the tourist island of Phuket.
My suggestion
Although rates may be high, I advise you to spend 1 or 2 nights in the national park. It's a chance to sleep in a floating hut on a lake, in a large adventurer's tent, or even in the trees, completely surrounded by nature.
Elephant rides have become a major concern in many locations, but are still offered by a handful of so-called "sanctuaries" with the proposition to get close to the exotic and majestic animal. Elephant rides are offered on every street corner and Westerners have little knowledge about the cruel methods to succeed in training these enormous animals.
To set the scene for you, imagine 2,188 km² covered by 80% forest and populated with more than 800 animal species roaming completely free. Add streams, waterfalls and a mountain range amongst 2,000 plant species. Classify it all as a UNESCO world heritage site and you have the Khao Yai national park.