Part of Thailand's tourist development strategy is to promote traditional festivals to an international audience. Which isn't to say they don't occassionally invent some new ones. Here's a list of the biggest festivals around Thailand. You can check out the Tourism Authority of Thailand's web site for more festivals and current information on most of these.
14 February - Underwater Wedding Ceremony
Although its not a traditional Thai holiday, Valentine's day is celebrated around the country anyway. In Thailand, they'll take any excuse for a party! Perhaps the most outlandish celebration is the mass Underwater Wedding Ceremony held in Trang province of southern Thailand. Every year, on 14 February, couples who want to can get married underwater.
January to February - Chinese New Year
Although not a national holiday, the Chinese Lunar New Year is celebrated all over Thailand. One of the biggest celebrations is in Bangkok's Chinatown, with the district's main road, Yaowarat, closed to traffic for several days.
14 February - The Elephant Banquet
The folks up in the northern province of Lampang have a strange way of celebrating St. Valentines Day. They put on a feast for elephants. The world's largest toke tables -- a round table usually less than three feet across -- are piled high with flowers, bananas, sugar cane and other elephant favorites, then the big beasts go at it. The elephants don't get to eat for free, they play music, sell their own paintings, etc.
March - Thai Kite-Flying Festival
Kite flying is a very old Thai sport. The monsoon rains, which usually start to arrive in Bangkok in late April, are preceeded by a month or more of light winds which are perfect for kite flying. During the month of March, you'll find several vendors selling kites at Sanam Luang, the huge open space in front of the Grand Palace, and you'll see many people flying kites, either alone or in competition with each other. In Thailand, kite flying is something of a contact sport!
1st Weekend in April - Phanom Rung Fair
The ancient Khmer temple of Phanom Rung in Buriram province of northeastern Thailand is the site of the huge Phanom Rung Fair, a sort of temple fair on a grand scale.
13 to 15 April - Songkran Festival
Without a doubt, the biggest party of the year is the annual Songkran Festival, celebrated throughout Thailand. The festival traditionally celebrates the end of the dry season, and has always involved water. In recent years, all out water fights have erupted in many tourist areas. The government has sought to tone things down a bit, but its still a big party, just a little drier. Chiang Mai remains one of the most popular places to be, but it doesn't really matter where you are.
Second Weekend in May - Rocket Festival
May is when the rains are supposed to start, but sometimes the clouds take a little coaxing to to release their liquid treasure. In the province of Yasothon in Thailand's northeast, they do their coaxing with rockets. There are competitions to see who can build the most beautiful and biggest rocket. We can pretty much gurantee you'll have a blast!
Sometime in June - Phee Ta Khon
Possibly Thailand's strangest festival, Phee Ta Khon might best be described as a sort of Halloween, only its adult men who dress up and not children. The costumes are meant to scare away ghosts who may be about and are sometimes a bit risque. The exact date of the festival is decided by a local shaman and may only be determined a few weeks before.
July - Beginning of Buddhist Lent
Traditionally, Buddhist monks retreated into their temples during the height of the rainy season in order to avoid harming any of the new life which springs forth during this time. The beginning of this period, for which most use 'lent' for lack of a better term, is celebrated throughout Thailand. The biggest celebration is in the town of Ubon Ratchatanee, where huge wax sculptures are created and put on show. The idea for these is that formerly, large candles were presented to temples at this time so that they would last through to the end of lent.
Late October or Early November - Vegetarian Festival
Although most guidebooks concentrate on the sideshow part of this festival as its celebrated in Phuket, the vegetarian festival itself is actually held throughout Thaialnd. For nine days, Thais of Chinese descent will eat only vegetarian meals.
Last Sunday in November - The Monkey Banquet
The town of Lopburi about two hours north of Bangkok is famous for its ancient palace, and its monkeys. As a form of merit-making, each year the chinese community of the town puts on a huge chinese banquet for the monkeys. Of course, being monkeys, you can guess at the kind of chaos that reigns.