If Thailand has a forest that deserves the word primeval, it may well be around Thap Lan. The park lies in the south-east of the Khorat plateau, between the Sankamphaeng range and the lowlands, and it is one of the pieces of the Dong Phayayen–Khao Yai forest complex that UNESCO listed in 2005. The name is said to come from a type of palm that grows in the area, and the park is known for its rich lowland rainforest, rare in a country where so much has been cleared for farming.
It is a place of waterfalls, caves, rocky streams and tall trees, with a good chance of seeing wildlife if you have patience and a guide. Elephants, gaur and clouded leopards live here, and the park is part of the habitat of the Siamese crocodile and various hornbills, as well as hundreds of species of butterflies. Pang Sida, its neighbour, is known for its cascades and wide views from the escarpment. Most visitors come on guided walks and wildlife safaris, and it is best to arrange these in advance through the park office.
Getting there is part of the pleasure. Roads from Khon Buri and the main highway toward Prachinburi are well surfaced and mostly straight, but the last stretches into the park can be narrower, with sharp bends and the occasional herd of cows. Heavy rain in the wet season, from May to October, can cause flooding, and the dry season brings cooler air and clearer skies, though it is also hotter at midday than you might want. Wildlife on the road is a real hazard, especially at dusk, and snakes are often seen basking on the warm asphalt.
Khon Buri is the nearest town of any size and has fuel and food, though it is around thirty-five kilometres from the park. Within the park there is a small visitor centre and some simple food, but it is best to carry water and snacks. A local guide is the best way to understand what you are looking at, and to avoid the dangers of wandering alone in forest that can be hot, humid and easy to get lost in.