The verdant Banthat Mountains, which run down the peninsula as far as the Malaysian border, mark the eastern boundary of Trang province. The forested higher elevations of the mountains, which rise to 4,430 ft (1,350 m) at Khao Ron, are one of the few places in South Thailand where the Sakai tribe still maintain their hunter-gatherer existence. These ethnically unique Negrito people speak a language related to Mon-Khmer. Traditionally they live in groups of 10 to 30 in simple lean-to leaf and grass shelters near running water, and hunt with poison blow darts. Forest clearance and exposure to lowland culture has led to some Sakai becoming agricultural laborers. The mountains are also home to many amphibian and reptile species, including dwarf geckos and wrinkled frogs. Rare birds include hornbills, spiderhunters, hawk cuckoos, and the narcissus flycatcher. A worthwhile excursion is to the Khao Chong Nature and Wildlife Study Center, 12 miles (20 km) east of Trang off Highway 4. It contains an impressive open zoo and two waterfalls. Just to the south, a bird sanctuary at Khlong Lamchan has a reservoir that attracts many species of duck. The minor road heading south along the western flanks of the Banthat Mountains gives access to a series of spectacular waterfalls, caves, and shady picnic places. Highlights in clude the huge Ton Tay falls, the spray rainbow that often forms by mid-afternoon over the Sairung falls, and the stalactites and stalagmites of Tham Chang Hai (“lost elephant cave”) near Muansari village in Nayong district.
Much farther south, and easily accessible from Satun, is the spectacular Thale Ban National Park