Fifty-two people were killed and 431 injured in 387 road accidents on Monday, the first day of a government campaign to reduce crashes during the Songkran festival.
Pol Lt Gen Anan Srihiran, assistant chief of the Royal Thai Police and spokesman for the government's campaign centre, said 36.7% of the traffic accidents were caused by speeding and 26.9% by drink-driving.
Just under 80% of the smash-ups involves motorcycles.
Chiang Mai province recorded the most accidents with 19. The highest death toll came in Prachin Buri where six were killed, and the provinces with the highest numbers of injuries, 23, were Chiang Mai and Udon Thani.