April 13-14 every year, mark Thailand's new year celebration every year.
It's also known as Water Festival of Thailand, locally called "Song Kran".
This year, Thailand sets World Largest Water Pistol Fight, took place at Bangkok Central World Shopping Plaza and the Bangkok Metropolitan Administration.
The counted number of water pistol shooters was 3,477. The fight lasted for 10 minutes.
Reference:
http://www.worldrecordsacademy.org/mass/largest_water_pistol_fight_Thailand_breaks_world_record_112209.html
