Official dates for Songkran are 13th to 15th April. Pattaya usually extends these days to more days and Pattaya also has a special 'Pattaya Songkran' on the 19th.
Craziest Days in Pattaya during Songkran are usually on the 18th - 19th of April. In Naklua the major water madness is on April 18th and in Central Pattaya the major water madness is on 19th April.