However long you plan to spend in the capital, it’s always worth setting aside time for its great showpieces: the Grand Palace and nearby Wat Pho. In the afternoon you’ll be free to explore at your leisure. If you can tear yourself away from the pool, we recommend a visit to Chinatown, with its busy street food markets and beautiful temples. A great place to eat after dark is Yaowarat Road, where you can tuck into steaming plates of dim sum, noodles in a pepper broth and of succulent, fresh seafood. Nearby Sala Chalermkrung Khon stages elaborately costumed performances of traditional Thai masked dance – a superbly exotic spectacle.

Maeklong Railway Market is so-named because it is held on the suburban rail tracks themselves: a siren sounds ahead of the arriving trains and all the stallholders hurriedly pack away their goods, replacing them after the locomotive has trundled through. Trips to Maeklong are conveniently combined with a visit to the floating market at nearby Danoen Saduak, where shoppers and vendors paddle around a gird of narrow, covered waterways.

Scattered amid lawned grounds on an island encircled by three rivers, the crumbling chedis (stupas) and Buddha images at the Ayutthaya Historical Park, 49 miles (80km) north of Bangkok, are all that remains of former capital of Siam, which at its height between 1350 and 1767 ranked among the wealthiest and most glittering cities all Asia. We always recommend an early start to enable visitors to see the park at its most evocative, with soft, early morning light burnishing its red-brick pagodas and gently smiling Buddhas, many of which are lovingly wrapped in bands of yellow silk.

Spread over 770 square miles (2,000 square km) of forested mountains, Khao Yai is laced with a network of tarred roads and well-defined trails that enable you to explore the area’s pristine forest 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.

Erected on the rim of an extinct volcano, with sweeping views south to the Dangrek Mountains on the Cambodian border, Phanom Rung is the most spectacularly sited of Thailand’s Khmer temples. The shrine, originally dedicated to Shiva, is surmounted by a magnificent tower, which during the full moon phase of April each year becomes the focus of an exuberant festival, when the stonework is adorned with vibrant silk streamers and banners. A 139-mile (225-km) highway, paved in laterite, once ran all to way from Angkor to Phanom Rung, and then north to Isaan’s other great Hindu shrine, Prasat Him Phimai, which you’ll see in the afternoon.

The best base for exploring the archaeological sites of southern Isaan is Surin, a town on the Khorat Plateau famous for two things: silk and elephants. The former is produced in many of the surrounding villages. Visitors are welcome to visit workshops and to watch artisans reeling thread from cocoons, dyeing the yarn and weaving it into beautiful scarves, sarongs and ties. Our preferred hotel is also one of the best places in the region to sample traditional Isaan cuisine.

The Elephant Study Centre at Surin was set up as a not-for-profit organization to rescue animals used in street begging, circuses and other occupations detrimental to their health. Rather than merely purchase the animals from their mahouts, which only perpetuates the cycle of cruelty (because the money is invariably used to by a new elephant!), the Surin Centre actually relocates the mahouts themselves, employing them to care for their elephants. Nearly 200 are now at the property, where visits can walk in the forest with and bathe the ellies – a heart-warming experience!

At the eastern extremity of Issan, on the Laos-Thai border, the small town of Khong Jiam clusters on the tip of a peninsula overlooking the confluence of the Mekong and Mun Rivers. The mingling of the different coloured waters (the Mekong is sandy brown and the Mun blue-green) forms an arresting natural spectacle known in Thai as ‘maenam song si’ (‘two-colour river’), best admired by boat or kayak.

A short drive upriver from Khong Jiam, the Mekong swings around a giant meander, carving a great slice from the sandstone bedrock. Protected as the Pha Taem National Park, the resulting escarpments, capped with stands of flowering trees and weird mushroom-shaped rock formations, harbour some of the finest prehistoric rock art in Southeast Asia – a lively assortment of geometric human figures, hand prints, animals, farming and fishing scenes rendered in red ochre. The paintings are believed to be 3,000–4,000 years old.