A three-hour drive north-east of Bangkok takes you to Thailand’s oldest-established and largest national park, Khao Yai. Spread over 770 sq miles (2,000 sq km) of forested mountains, the sanctuary is laced with a network of tarred roads and well-defined trails that enable you to explore the area’s pristine jungle and, with luck, encounter some of its wildlife. Species you can be confident of sighting on a day visit include hornbills, gibbons and macaques, along with an assortment of giant spiders, squirrels, gaur (bison) and superb butterflies.