Sai Yok Yai
This is a waterfall fit for a king. Indeed, King Rama V once visited this site and it's been praised in Thai songs and poems. The falls are found within the Sai Yok Yai National Park, but are set back 3 km from the road, so be prepared to do some walking or to hop on a motorbike. You can board a boat and ride the rapids at the falls, or skim along the river between the towering rock walls.