Khao Yai National Park covers more than 2,000 square kilometers of forest and grassland in central Thailand. More than 50 km of hiking and biking trails wind through the long-standing nature preserve, and its many waterfalls include 150m-tall Haew Narok and 20m-tall Haew Suwat, immortalized in the D See more.anny Boyle film 'The Beach.' . Hide this content