Khao Yai is Thailand's oldest National Park. It is about 165 km north ofa Bangkok nd 2 hours by car and spanning the four provinces of Nakhorn Ratchasima, Nakhon Nayok, Saraburi and Prachin Buri. DISTANCE :• From Bangkok 165 km. • From Muak Lek 34 km. • From Thanarat Rd. 30 km.