Songkran is the Thai New Year's festival. It is celebrated on the first after the first new moon of April. Everything shuts down for the Songkran festival and then a country wide water fight emerges. Make sure that anything electronic is put in a plastic bag because you are going to get soaked. People roam the streets with bowls of water, water guns or even a garden hose, and drench each other and passersbys. Some even mix colored powder into the water. As a tourist, you are a target for sure. Khaosan Road is particularly crazy and is a must see for this time. The festival lasts officially for 3 days in the Bangkok area.
This tradition originated in the lustration ceremony, in which the Buddha images in the temples are cleaned. In many cities, such as Chiang Mai, the Buddha statues from all of the wats in the city are paraded through the streets, so that people can throw water on them as they pass. The use of plaster is also very common having originated in the plaster used by monks to mark blessings.
Other traditional elements of the festival include young people visiting elders, and pouring small amounts of lustral water on the hands of their elders as a sign of respect. People carry handfuls of sand to their temple in order to make up for the dirt that they carry away on their feet during the rest of the year. The sand is then piled into large, tiered sand castles and decorated with colorful flags. In general, Songkran is a time for cleaning and renewal. Many Thais take this opportunity to give their home a thorough cleaning.