Capital of the province that bears its name, Trang is not a must see in itself, but, with a bit of effort, can be fun.
My suggestion
If you're there during Loi Krathong (the November full moon festival), make sure you enjoy the celebrations at the Buddhist temple. It's beautiful, fun and laid back.
The Khong Chiam region is still largely unaffected by tourism and, for those willing to explore it, offers spectacular scenery and the promise of peaceful days spent well away from the noise and chaos of the urban environment. With its waterfalls, cliffs and rock paintings, Pha Taem is the kind of place you simply never tire of exploring.
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.