Khao Sok National Park is an amazing refuge for virgin tropical rain forest. Though it's hard to fact-check, it's often said that this park alone is more diverse than the Amazon Basin Rainforest. Whether that's true or not, it's certainly an indication of the kind of biodiversity in the area.
This trail splits off of the Khao Sok Main Trail where it intersects with the Orchid Trail. It heads north, continuing to follow the Sok River. The path can be more difficult, often requiring scrambling over large roots and muddy puddles. Many side trails to the river offer wonderful respites from the dense jungle, and the peaceful Ton Kiol waterfall at the end is a nice place for lunch.
Along the path, you'll pass an amazing tree, one of the largest that I've seen. It has a name, though I've forgotten what it is. Stop to admire the huge roots, but don't get lost in the side trails that cross around here! Climb up over the tree roots to stay on the main path.