When I first arrived in Thailand I had no idea that I was going to be there for the Songkran Festival. I will say however that I reccommend to anyone traveling to Thailand that you must travel in April so you can experience this Thai New Year. At first you have to get used to being wet all the time. Then you have to join in the festivities. If you are not particularly fond of getting wet then I would suggest staying inside until night time. They only through water during the day light hours. and they do this for five days.
But it is great to walk around Chiang Mai (the heart of Songkran). people from all over thailand come to Chiang Mai for Songkran because of the canal that is around the city. Perfect supply of water for throwing. And at night time on the weekends at the market places they pay money to pay respects to buddha by pouring water over his statue.
All in all a fine time of year to experience culture first hand.