Bangkok

Bangkok proper is governed by an elected Governor and its own metropolitan council, with no province above it — an arrangement unique in Thailand. The Bangkok Metropolitan Region adds five neighbours, and each holds something the city itself does not. Nonthaburi to the north-west is inner suburb, now stitched on by the metro's Purple Line. Pathum Thani to the north carries much of the university and research belt, along with the northern commuter corridor. Samut Prakan to the south holds Suvarnabhumi airport, the open-air heritage park at Ancient Siam, and a gulf-side recreation area where migratory birds gather in the cool months. Samut Sakhon to the south-west runs the country's largest commercial fishing port at Mahachai, and the branch railway that produces the region's most photographed market. Nakhon Pathom to the west has the Phra Pathom Chedi, the tallest Buddhist stupa in the world and the oldest Buddhist monument in the country, its present structure raised in the nineteenth century over a far older core. Together the six hold around a third of Thailand's economy — and for a visitor the practical point is that the metro, Skytrain and commuter rail now reach into three of the five, which turns several of these from excursions into afternoons.

Bang Krachao is an oxbow island in the Chao Phraya, barely three kilometres from central Bangkok as the heron flies and a different country in tempo. Twelve square kilometres of orchard, mangrove and rehabilitated wetland inside an exaggerated river meander, it was protected as a green zone rather than developed, and it is now crossed by an elevated cycle path running for kilometres through the canopy, with a weekend floating market at Bang Nam Phueng and a large botanical park with birdwatching towers. The classic approach is the small longtail crossing from the Bangkok side, bicycles hired in the village by the pier — the island is flat, shaded and almost carless, which makes it the best cycling in the metropolitan area by a wide margin. Further south, the same province holds Ancient Siam, an open-air park laid out in the rough geographical shape of Thailand with reduced-scale reproductions of the country's significant monuments placed in their real positions, and the Erawan Museum with its enormous three-headed bronze elephant standing over a collection of Buddha images and Asian antiquities. All three make comfortable half-days from the city.

South-west of the capital, three markets make the standard day out and they are genuinely different from one another. Damnoen Saduak in Ratchaburi is the photographed one — loaded sampans, noodle soup cooked from the boats, stilt restaurants along the canal — and it repays an early start: the working market happens at dawn, and by late morning the bargaining is entirely for visitors. Amphawa in Samut Songkhram is the locally attended alternative, an evening market on a working canal in a real town, busiest from Friday to Sunday afternoon into the night, with boat trips at dusk to see fireflies in the riverside trees in the wetter months. Four kilometres away, the Mae Klong railway market is the region's oddest sight: stalls and canopies set up directly over a working railway track, folded back several times a day as the train eases through within centimetres of the produce, then folded out again behind it. The branch line that produces this is itself part of the experience, and a rail-and-ferry circuit through Mahachai and Mae Klong makes a full day where the journey is the point. Don Wai in Nakhon Pathom, a riverside market with a long row of food stalls, is the least touristed of the four.

Eighty kilometres north lies Ayutthaya, the Siamese capital for more than four centuries until its destruction in 1767, and the model on which Bangkok was deliberately founded afterwards. At its height it was among the largest cities in the world, a moated island at the meeting of three rivers with resident embassies from France, the Dutch East India Company and Portuguese Macau, and its ruined brick-and-stucco temples have been UNESCO World Heritage since 1991. From a Bangkok base it is the easiest of the major day trips: mainline trains run frequently from the central station and take around ninety minutes, minivans slightly less, and the historic island is small enough to circle by bicycle once you arrive. The ruins themselves — what the two capitals meant, how to read the temples, and whether to come for a day or stay the night — are covered in the Ayutthaya and Sukhothai guide, and the modern town that lives beside them is its own destination.

A hundred and thirty kilometres west, where the plain gives way to the hills along the Myanmar border, Kanchanaburi is best known for the Bridge over the River Kwai and the wartime railway it belongs to — a line driven through this country during the Second World War at great human cost, and now one of Southeast Asia's most visited places of remembrance. The bridge stands and can be walked. The Thailand-Burma Railway Centre and the JEATH War Museum in town, the war cemeteries, and the Hellfire Pass Memorial in its rock cutting some way north-west all exist to hold that history for visitors, and the memorial museum in particular is the place to spend real time if the railway is why you came. Part of the original line still carries passenger trains from Kanchanaburi up to Nam Tok, a couple of hours through the hills and across a surviving timber viaduct above the river — the most direct way to understand the terrain the line was cut through. The province is not only its wartime history: Erawan National Park's seven-tiered waterfall, with pools you can swim in on the lower levels, is one of the finest in the country, and the parks further up the valley hold caves, more falls and a much quieter register.

A hundred and sixty-five kilometres north-east, Khao Yai was Thailand's first national park and remains the largest continuous forest in the interior — a couple of thousand square kilometres of evergreen and dipterocarp forest on the Khao Yai massif, inscribed by UNESCO as part of a wider forest complex spanning four provinces. Its wildlife is the reason to come: several hundred wild elephants, the country's densest inland population, along with gaur, sambar, gibbons, hornbills and a scattering of predators that visitors essentially never see. Elephants are genuinely often encountered on the park road at dawn and dusk, which is both the attraction and the reason to keep your distance and stay in the vehicle. The main trails run to the two well-known waterfalls — one an easy walk from a campground, the other a much taller drop reached by a longer path and a long flight of steps — with a longer forest hike to a viewpoint over the salt licks where the large mammals gather. The cool dry months are the practical season, and the park is also one of Thailand's designated dark-sky sites, which makes an overnight on the plateau worth more than a day trip.

Two hundred kilometres south-west on the Gulf coast, Hua Hin is the original Thai seaside resort and still the one with a royal address: a summer palace built here in the 1920s, and a town that has grown up around it under a height limit that keeps it low-rise. That history gives it a completely different character from Thailand's international beach destinations — the beach arc is used mostly by Thai families on weekends out of Bangkok, the old railway station keeps its preserved royal waiting room, and the grand railway hotel from the 1920s still operates on the seafront. Trains run down from Bangkok several times a day and the road journey is comfortable, which is what makes Hua Hin the natural long-weekend extension of a capital-based trip rather than a separate holiday. South of the town, a national park on the coast holds the much-photographed cave with a royal pavilion standing in a shaft of daylight beneath a collapsed roof. Hua Hin's own city guide serves anyone treating it as a destination rather than a day out.

Almost everything above runs off the rail and bus network radiating from the capital, and the single most useful fact is that the long-distance hub moved: Krung Thep Aphiwat Central Station, the large terminal north of the centre, has replaced the old Hualamphong station for mainline services. Trains for Ayutthaya and the north, for Pak Chong and Khao Yai, and for Hua Hin and the south all leave from there, while the separate Thonburi station on the west bank serves the Kanchanaburi line, and the branch line to the Mae Klong markets starts from Wongwian Yai. Inter-provincial buses run from three terminals — northern services from Mo Chit, eastern from Ekkamai, southern and western from Sai Tai Mai — with minivans covering the same destinations faster and departing more often. How Thai intercity transport works in general, including which mode suits which distance, is set out in the getting around Thailand guide. For the day-trip orbit specifically, the rule of thumb is that anything within about two hours works comfortably as a day out, and anything beyond it is better as an overnight.