Khao Yai National Park Nakhon Nayok, Prachin Buri and Saraburi, Thailand's first national park. Considered a world natural heritage of the two of Thailand, he is able to see wildlife large and small varieties are also waterfalls, beautiful More than 20, including the hiking trails, nature study, another 13 routes so. a favorite of those travelers who like to experience nature up close throughout all ages.