Walking along the dimly lit 280m trail through Lawa Cave you'll pass several large chambers with imposing stalactites, stalagmites and other odd rock formations. Bring a torch (or try to borrow one from the rangers) for the full experience. Sai Yok National Park admission fees apply (show your ticket if you've been to other sights the same day). It's signed along country roads 20km from Nam Tok Sai Yok Noi.
The cave is a short way from the river, and you can reach it by boat from Pak Saeng Pier, next to Boutique Raft Resort. It takes one hour and around 1200B to go there and back.