The death toll had been 264 last year.
The northern province of Chiang Rai reported the highest number of fatalities, 17, Bangkok Post quoted Interior Minister Anutin Charnvirakul as saying at a press conference.
Speeding, driving under the influence of alcohol and cutting in front of other vehicles were the main causes of accidents, he added.
Traditionally, thousands of tourists from across the world flock to Thailand to celebrate the water fighting festival, which was added to the UNESCO list of intangible cultural heritages of humanity last year.