Explore the depths of a cave
You can channel your adventurous spirit and explore one of the many pitch-black caves (with a guide, of course) of varying intensity levels within the jungle. Some are milder — not as deep with very little climbing — while others warrant a vast amount of physical exertion and even some swimming. There is no artificial lighting whatsoever, but your guide will provide the headlamps.
Be warned: you will likely see some creepy-crawly creatures inside the depths of the cave, namely giant spiders and bats. I personally found the bats adorable, but the six- to eight-inch spiders made me squirm, much to the amusement of both my fiancé and our guide! Luckily, Khao Sok's cave spiders actually glow in the dark, allowing you to spot them right away.