Phu Chong Nayoi National Park

Ubon Ratchathani Province

One of Thailand's wildest, remotest corners, the 'Emerald Triangle' is where the Thai, Lao and Cambodian borders converge. Most people visit this little-known 686-sq-km national park to see a pair of waterfalls, but there's some good stargazing and trekking too. For the latter, you must go with a ranger and it's best to call and arrange this before you arrive. You must have your own vehicle to get here.