Khao Yai National Park

Up there on the podium with some of the world's greatest parks, Khao Yai (อุทยานแห่งชาติเขาใหญ่) is Thailand's oldest and most visited national park. Covering 2168 sq km, Khao Yai incorporates one of the largest intact monsoon forests remaining in mainland Asia, which is why it was named a Unesco World Heritage site (as part of the Dong Phayayen–Khao Yai Forest Complex). But despite its size, it's one of the easiest national parks in Thailand for independent travellers to visit.