More about Songkran festival:
The Songkran festival (Thai: สงกรานต์ (Pronunciation), Khmer: សង្រ្កាន្ត; from the Sanskrit word saṃkrānti, or literally "astrological passage") is celebrated in Thailand as the traditional New Year's Day from 13 to 16 April. It coincides with the New Year of many calendars of South and Southeast Asia.
The date of the festival was originally set by astrological calculation, but it is now fixed. If these days fall on a weekend, the missed days off are taken on the weekdays immediately following. Songkran falls in the hottest time of the year in Thailand, at the end of the dry season. Until 1888 the Thai New Year was the beginning of the year in Thailand; thereafter 1 April was used until 1940. 1 January is now the beginning of the year. The traditional Thai New Year has been a national holiday since then.
Songkran has traditionally been celebrated as the New Year for many centuries, and is believed to have been adapted from an Indian festival. It is now observed nationwide, even in the far south. However, the most famous Songkran celebrations are still in the northern city of Chiang Mai, where it continues for six days and even longer. It has also become a party for foreigners and an additional reason for many to visit Thailand for immersion in another culture.