Tham Pha Tup Forest Park

Two limestone towers rise from rice fields west of the highway, enclosing a small valley with forest trails, caves and viewpoints. Villagers have long noted that these hills are limestone, unlike the mountains around them.

The name comes from the northern word "tup", to slump or sink. The abbot of Wat Pha Tup told a 2006 blog that the peak was once so tall you could see all of Nan from it, until the mythical hatsadiling bird landed on it and the mountain sank. Another legend says Pu La Hueng, a giant of Doi Phu Kha, was carrying two mountains, Pha Tup and Pha Khwang, as a gift to Nan, but met a white-headed bird that said it had flown until its head turned white without reaching the city, so he gave up and set the mountains down here. Both are folk tales.

The Royal Forest Department declared Tham Pha Tup Forest Park in 1978; tourism sources give 1 October 1978, and one calls it the first forest park in Nan. Wikipedia gives a gazette date of 24 December 2020, possibly a re-listing under the 2019 National Parks Act, but this is unconfirmed. Three area figures exist: 521 rai in a 2023 academic article citing the park office's 2019 data, 528 rai in tourism sources, and 1.2 km² (about 750 rai) on Wikipedia, so roughly 520 rai is a fair figure. It is managed by the national parks department through Protected Area Regional Office 13 in Phrae.

Sources disagree on the number of caves — usually about seven, with counts from six to eleven. Named ones include Tham Phra, Tham Pha Sawan, Tham Pha Tup, Tham Chedi Kaeo, Tham Bia and the sacred pool, Bo Nam Thip.

Tham Pha Sawan, also called Tham Phra, is about 110 m long and 22 m deep: an entrance gallery, a 30 m side passage, two large gongs on a wooden frame, a passage of about 40 m ending at two Buddha images, and a 4 m climb to a chamber with a skylight about 30 m across. François Brouquisse first explored it in 1992 and it was mapped in 2008.

The caves have a long survey history. After François Brouquisse's first exploration in 1992, Tham Pha Tup appeared in Dunkley's The Caves of Thailand in 1995. The UK Shepton Mallet Caving Club visited in December 2003 and surveyed again in March 2013. From 12 July to 5 August 2008 the French club SSAPO's four-person "Nanthai 2008" expedition, led by Philippe Jarlan, visited 16 caves in Nan and Chiang Mai, mapped 8 and published its report in 2010. The Grottocenter database records at least six caves in the park.

Tham Pha Tup is about 50 m long, with a very narrow entrance opening into a large, sparsely decorated hall. Tham Bo Nam Thip is about 100 m long and 50 m deep, entered by ladder, with a Buddha image beneath a shaft open to the sky; villagers hold its pool to be sacred and full all year, but a 2020 survey found it nearly dry and littered with plastic. Tham Chedi Kaeo is about 43 m long and Tham Bia about 25 m.

Tham Phra matters most to villagers: every year on the 15th waxing day of the northern fifth month they climb up to gild the Buddha image and make merit, a tradition Kasetsart University researchers call the Pha Tup cave-climbing festival.

The caves also have scientific value: Tham Pha Sawan is the type locality of the cave millipede Plusioglyphiulus bessoni, first described from here, and on 20 August 2020 a black-bearded tomb bat (Taphozous melanopogon) was recorded in Tham Pha Tup.

The Ban Pha Tup community around the park manages more than 6,000 rai of bamboo forest in the reserve and community forest. Bamboo is the village's signature resource, looked after by weaving, elderly and bamboo-conservation groups. Studies in 2021–22 found nearly half of villagers revere Chao Pho Pha Tup as their main guardian spirit, and see Wat Pha Tup and the cave as centres of faith.

In 2005 students from Uttaradit Rajabhat University's Nan campus and the Pha Sing subdistrict council ran participatory community-economy research at Ban Pha Tup; accounts from that time mention a stone-crushing plant and a rubber research centre near the caves.

No evidence has been found of archaeology, Second World War use or communist insurgency at Tham Pha Tup. A 2023 survey of Nan's prehistoric sites by the environment policy office covered the Phu Sang–Bo Suak area, not Pha Tup.

A trail-map board stands at the car park and the paths are surfaced, though some visitors report poorly maintained stretches, fallen trees and the odd snake. The caves are unlit, so bring a torch and closed shoes.

Entry is free and the park opens about 08:00–17:00; allow half a day. The dry, cool months of November to February are easiest for walking, while in the rains fallen leaves make the paths slippery.