Forty-one people were killed and 500 injured on the first of the "seven dangerous days" of New Year holiday travel on the country's roads, officials said on Friday.
The 477 accidents recorded on Thursday compared with 524 accidents that resulted in 42 deaths and 565 injuries on the first day of the year-end travel period 12 months ago.
Officials estimate that 2.5 million people and 750,000 vehicles left Bangkok on Thursday for destinations across the country, Transport Minister Arkhom Termpittayapaisith said.
Chiang Mai recorded the highest number of accidents with 23 and injured people with 25 while Si Sa Ket had a nation-leading six deaths on Thursday.
The most common cause of road accidents (42.8%) was drink-driving, followed by speeding (26%). Motorcycles were involved in 73.6% of the accidents.
The most common time for accidents was between 4pm and 8pm. Officials said 52.5% of those killed and injured were of working age.
The Transport Ministry said this week that it aimed to reduce fatalities this year by at least 5% from the 487 recorded during the "seven dangerous days" a year ago.
Thailand has the world's second-worst road fatality rate per 100,000 population, behind only Libya, according to a World Health Organization study.