Bangkok is best in the so-called cool season (expect a mere 30 degrees), from November to February. It starts to get hotter through February, typically reaching a 40 degree climax in April and May, before the rains arrive. It’s still warm, though wetter, from June to August. At the end of the rainy season (September - October), whole districts of the city can flood, and there is frequent disruption.
The eastern islands (Gulf of Thailand) are affected by the northeast monsoon from October to December, with the worst of the rains coming in November. Travel to/from the island can be difficult during these months. January to April is high season, with hot and humid days; May through September are cooler, with pleasant breezes spilling over from the southwest monsoon during July - September.
The east coast of peninsular Thailand follows the same pattern, but the October - December monsoon is much milder; and there is also a little rain and cloud spilling over from the western monsoon (July - September). But it is rarely very wet at any time of year.
The west coast and islands (Andaman sea) have peak season in November to February, when the weather is relatively cool (30 degrees) and there is little rain. From March it warms up, and then comes the monsoon season (May - October). The seas can get very rough and you can expect some strong but short downpours (especially in May, June and September).
The north mainland (e.g. Chiang Mai) is best from November to January, when it's quite cool (high 20 degrees) and clear. But it is very busy. In February and March, swidden (brush) fires make it hazy in the hills, and low waters rule out rafting, but it's still fine for city sight-seeing. March to May is hot and humid, with rains typically coming any time after the Songkran festival (mid April). June to October is consistently rainy, making trekking muddy work, but ideal for rafting.
Festivals and events in Thailand are particularly colourful and vibrant, and it can be worth planning your trip to coincide with one. The 2 biggest - book early, or avoid them altogether! - are Songkran (New Year) in mid-April, which is basically an excuse to throw water at complete strangers; and Loy Krathong (Festival of Lights) in November, when Thais send floats downriver with a coin, candle and incense to take bad luck away. You'll also need to book hotels in advance if you plan to be in Bangkok around Chinese New Year (which falls on the first day of the Chinese Lunar Calendar every year) or Losar (Tibetan New Year). During the rest of the year, handicraft shows, beauty pageants and boat races are also popular. Many are determined by the lunar calendar, so the dates change from year to year.
Note: flight, boat, train and bus timetables change constantly, and airlines come and go, so please do not rely solely on this information for your travel planning. Check with relevant companies, or a flight search engine like Skyscanner, first.
FROM THE UK
It's a 12-hour flight to Bangkok (BKK) - more if there's a connection involved - and what with the 7-hour time difference, you should basically reckon on a full day for the outward journey. Check the seat pitch (legroom), and factor in a day or so to get over the jetlag. Coming back, it effectively takes 5+ hours, and the jetlag means you fall asleep before supper and wake up before dawn.
There are direct flights from London Heathrow with Thai Airways, British Airways, and Qantas (the latter 2 codeshare). Cheaper flights are sometimes available with the Taiwanese carrier Eva Air from London Heathrow.
There are also a number of airlines that have indirect flights such as Emirates (from London Heathrow or Gatwick via Dubai), Kuwait Airways (from London Heathrow via Kuwait), Etihad Airways (from Gatwick via Abu Dhabi). These maybe a little cheaper than the direct flights but can take anything from 14 to 20 hours each way. But you may be able to use Air Miles, or make something of the stopover en route.
There are also charter flights to Phuket (HKT) in high season (November-March), though this usually restricts you to a 7- or 14-night stay, and includes accommodation in a charmless, mainstream hotel. Of course, if you find a really good deal, you could take the package and ditch the accommodation; or use the first night for post-flight recovery, then branch out on your own.
There are direct flights with KLM from Amsterdam, Lufthansa from Frankfurt, Alitalia from Rome, Air France from Paris, Finnair from Helsinki, Swiss from Zurich.
These flights are also useful for those wanting to fly from a regional UK airport to a European hub (e.g. Amsterdam, Frankfurt, Rome) and continue to Bangkok from there.
All flights are at their busiest and most expensive over Christmas and New Year, with July and August also popular.
All of these flights can be booked through the airlines' websites, through an online consolidator like Expedia, Opodo or Traveljungle, or through a traditional travel agent. Note that some online consolidators exclude Eva Air, with the notable exception of Traveljungle, which trawls airlines and agencies alike, to come up with a wider (though not always up-to-date) 'catch'.
FROM USA AND CANADA
From North America there is now a direct flight from Los Angeles (LAX) to Bangkok with Thai Airways. For other cities there are dozens of options entailing just one stop en route. From the west coast it is normal to fly via Asia (e.g. LA or Vancouver via Tokyo, Taipei or Hong Kong), taking 18-20 hours. From the east coast you fly via Europe (e.g. New York or Montreal via Paris, Zurich, Amsterdam or London), taking 20-22 hours.
Airlines include Air Canada, Air France, Cathay Pacific, China Air Lines, Delta Airlines, Finnair, Japan Airlines, KLM/Northwest, Swiss International, Thai Airways and United.
Check the seat pitch (legroom), and factor in a day or two to get over the jetlag. Flights are at their busiest and most expensive over Christmas and New Year, with July and August also popular.
In addition to Thai Airways and other national carriers' networks:
Orient Thai (also branded as 'one-two-go') flies direct from Hong Kong to Bangkok.
Bangkok Airways flies from Guilin, Siem Reap, Luang Prabang, Male (Maldives), Phnom Penh, Trat and Yangon to Bangkok; and from KL and Singapore direct to Samui.
Internal flights are quite cheap and can save a lot of time and hassle compared to bus or train journeys.
We flew with Bangkok Airways from Samui - Sukhothai - Bangkok and found them to be very punctual and efficient. The airline also co-owns Samui's exotic little airport, which must be one of the most laid-back ways of starting a holiday: open-sided salas, thatched roofs and dinky little shuttle "trains" make it feel more like a funfair attraction than an airport.
Bangkok Airways operates a growing network of flights including:
Bangkok-Trat (Koh Chang)
Samui-Pattaya (U Tapao)
Some of these cities are also linked by direct flights to each other.
Thai Airways flies from:
Some of these cities are also linked by direct flights to each other.
Orient Thai, a newer budget airline, flies from:
Thailand has a reasonably wide, fairly slow and very cheap rail network, which is fun if you are not in a hurry. The most popular route is the overnight sleeper train from Bangkok to Chiang Mai, which is an atmospheric way to arrive in the north - though of course you can see more from the (slower) day-trains. Other useful routes include the line south from Bangkok past Hua Hin and Pranburi to Chumphon (for Koh Tao); and indeed on to Surat Thani (for Koh Samui) and Nakhon Si Thammarat, if you don't mind spending a full day on board.
The best part is sharing your carriage with friendly local people, including monks, schoolkids and a constant flow of people selling snacks and drinks: sticky rice cooked in bamboo stems, packaged rice and seafood stir-fries, fresh pineapple and mango. There's no air-con, but the breeze is usually enough, and frankly, for a few dollars per long-distance journey, what do you expect?
There's a good network of inter-city bus routes, but they are rather slow and can be uncomfortable for long journeys. Some are air-conditioned and cost a bit more (but still not much). On the whole, the cost of private car transfers is so reasonable that it is amply worth the extra for the added comfort and flexibility in timing.
On more popular country routes, you'll find minibuses, usually with air-con, which cost a little more money and take a little less time than the buses, though they can get cramped when full.
WITHIN TOWNS AND CITIES
You'll see songthaews - pick-up vans with 2 benches in the back, which give them their name - in most towns. Most operate along fixed routes, but they are also available for private hire (as a taxi) if you want. Fix your fare before setting off.
Standard taxis are also available in Bangkok and the larger cities, colour-coded according to whether they have air-con or not.
Another option - certainly more colourful, but the charm does wear off - is the three-wheeled tuk-tuk, named after the sputter of its little two-stroke engine. These are only available on a private hire (taxi) basis, and often cost more than an ordinary taxi, unless you bargain hard. And they're not particularly comfy - you and your luggage swing perilously around, dodging vehicles and pedestrian, but not evading the traffic fumes. But you have to try one at least once - and some hotels have their own, genteel, chauffeur-driven tuk-tuk for a gentle baptism.
Finally, if you're desperate, you can hop onto a passing motorbike-taxi, whose drivers wear brightly-coloured and numbered bib-jackets. They are supposed to supply a helmet for their passenger, but don't always do so.
Generally, if you can avoid road travel, do. It's rarely very quick or comfy in Thailand. In Bangkok, there is the Skytrain and the Metro, in addition to longtails and canal-boats - see our city guide for details.
Among the islands and the coastal areas such as Krabi, the easiest way to get about is by boat, either by (shared or private) 'longtail boat', or on a larger ferry-type service.
Longtails are everywhere, and are the aquatic equivalent of buses or taxis - that is, you can hire them for private charter, or catch one on a fixed route. They use loud diesel engines taken out of trucks and vans, and the driver sits on a box to steer the long rudder handle. Be prepared to wade/jump in, as there may be no ladder or landing pier. Unless it's an established route, we recommend fixing your fare before setting off.
Ferries ply between the major islands and ports, including Phuket - Koh Phi Phi - Ban Laem Kruat (for Krabi) - Koh Lanta on the west (Andaman) coast; and Koh Samui (Nathon or Big Buddha) - Koh Phangan (Thong Sala or Hat Rin) - Koh Tao - Chumphon (mainland) on the east (Gulf of Thailand) coast. See the regional descriptions and hotel (Getting There) pages for more details.
tourismthailand.co.uk - the Tourism Authority of Thailand in Britain