If you are interested in nature, this is your place. The Peninsular Botanic Garden (Thung Khai) is loaded with trees, flowers, plants, animals, and creepy crawlies. The garden is rather large and features a botanical garden, a herbal garden, a botanical library, a plant museum, and a canopy walkway The walkway is 175 meters long. You start out walking into lowland jungle (getting your little warning sign along the way) and eventually reach the canopy walkway. The walkways has three levels of height (10, 15 and 18 meters) and five walkways.
Trang is off the beaten tourist path in Thailand, but not difficult to get to. Buses and vans make their way to coastal areas and there are certainly drivers that will take you to the Botanical Gardens if you want. Admittedly, there are not many people that visit (at least that I saw) and it is a rather simple jungle walk. However, if you are into this sort of thing then it is a nice visit. You probably only need 2-4 hours max to see everything. I did it in two hours.