Some Holidays

Makha Bucha: commemorates the spontaneous gathering of thousands of people before Buddha who were enlightened by the event.
Songkran: celebration of the Thai new year, known as the “world’s largest water fight” lasting for 3 days to wash away the sins of the prior year
Loy Krathong: a thank you offering to the river goddess who gives life to people by floating flowers and candle laden banana leaf floats

(source:http://www.unseenthailand.org/)