Thailand's first national park lies just a couple of hours from Bangkok, and it still has wild elephants walking down its roads. Khao Yai, established in 1962, covers a large area of forested hills on the southern edge of the Khorat plateau, and together with neighbouring protected areas, it forms the Dong Phayayen-Khao Yai Forest Complex, listed by UNESCO in 2005. The forests here are a mix of evergreen and deciduous, grasslands and streams, home to elephants, gibbons, hornbills, deer, and a small number of tigers.
The main road through the park climbs from the southern entrance near Pak Chong up into the hills, with tight, steep curves, good surfaces and lush forest on both sides. At the top, side roads lead to waterfalls, viewpoints and visitor centres. Haew Suwat waterfall is famous for its appearance in the film The Beach, and Haew Narok, a series of high falls, is impressive in the rainy season. Watch out for macaques by the roadside, which can be aggressive, and for elephants on the road, especially in the evenings. If you meet one, stop, keep your distance and give it time; never try to pass close.
The roads are open to motorcycles, though there is an entrance fee and sometimes restrictions on hours, particularly at night. Speeds are strictly limited to protect wildlife. The best time to visit is during the cool season, from November to February, when the air is fresh and the skies are clear; in the rainy season, from May to October, the forest is lush and the waterfalls are at their best, but the roads can be slippery and leeches lie in wait for anyone walking in the forest.
Outside the park, the area around Pak Chong has become a popular weekend escape for Bangkok residents, with resorts, cafés, farms and vineyards in the cool hills, which produce some of Thailand's best-known wines. On weekends and holidays, traffic can be heavy. The road along the northern edge of the park and the quieter routes toward Wang Nam Khiao offer good riding through farmland and forest.
Pak Chong has fuel, shops and restaurants of every kind, and Khon Buri, around thirty kilometres away, is a smaller town to the north-east. Try som tam, the spicy papaya salad of the north-east, with grilled chicken and sticky rice, and finish with a glass of fresh milk from the dairy farms of the area, a local specialty.