In Sai Yok National Park (อุทยานแห่งชาติไทรโยค), mountains reach as high as 1125m and limestone caves burrow beneath the ground. Hemmed by Mae Nam Khwae Noi, this 958-sq-km preserve doesn't have waterfalls as impressive as those in Erawan National Park, but it receives a fraction of the visitors. Home to rare wildlife, it's a bucolic place of walking trails amid mixed forests of bamboo, evergreen and deciduous greenery. For total immersion in nature, there are simple riverside bungalows where you can listen to a chorus of birdlife as the sun sets.
It's easy to explore Sai Yok independently, thanks to several sights (including waterfalls) reached along well-marked and maintained trails leading directly from the visitor centre. Many trails are open to bikes. The park's elevated location means temperatures are fresher than in surrounding towns, adding to the enjoyment of hiking or biking.