Located in the Um Phang Wildlife Sanctuary, this waterfall is Thailand’s largest, measuring an estimated 200m high and up to 400m wide during the rainy season.

You can camp (30B) at the sanctuary headquarters, although you’ll have to bring your own tent, and it’s best to book ahead from November to January. This is also the only time of year the sanctuary’s basic restaurant is guaranteed to be open.

Thais, particularly fanatical about such things, consider Nam Tok Thilawsu to be the most beautiful waterfall in the country. There’s a shallow cave behind the falls and several levels of pools suitable for swimming. The best time to visit is after the rainy season (November and December) when the 200m to 400m limestone cliffs alongside Mae Nam Klong are streaming with water and Nam Tok Thilawsu is at its best.

The easy 1.5km path between the sanctuary headquarters and falls has been transformed into a self-guided nature tour. Surrounding the falls on both sides of the river are some of Thailand’s thickest stands of natural forest, and the hiking in the vicinity of Nam Tok Thilawsu can be superb. The forest here is said to contain more than 1300 varieties of palm; giant bamboo and strangler figs are also commonplace.

The vast majority of people visit the falls as part of an organised tour, but it’s also possible to go more or less independently. If you’ve got your own wheels, take the turn-off to Rte 1167 just north of Um Phang. After 12km, turn left at the police checkpoint onto Rte 1288. Continue 6km until you reach the sanctuary checkpoint, where you’re expected to pay the entry fee. It’s another 25km along a mostly paved road to the sanctuary headquarters.

It’s easy to book a truck just about anywhere in Um Phang (round trip around 2000B). Alternatively, you can take a Poeng Kloeng–bound sŏrng·tăa·ou to the sanctuary checkpoint (30B, hourly from 6.30am to 3.30pm), and organise transport from there (round trip around 1800B).