Thai New Year falls on the 13th of April, beginning of raining season.
Wikipedia says: “Home Buddha statue is washed with pure water and petals of rose and jasmine. This day Thai youth pouring water on each other.”
No way! All tourist cities become mad and everybody pours water on each other. From dawn till tusk. Type “song kran” and you’ll see what it is. Sometimes fire truck drives the street and pours everybody with water jet, and well… it’s normal.
Never take any expensive items, cameras, lot of cash, etc. on the street, while Song Kran. Another option is small hermetically fastened handbags, but still you won’t put lot of items there. Remember that there is no escape from celebration for a whole week. So be advised.