The Cabinet on Tuesday announced May 4 as the new Coronation Day official holiday.
The new holiday date marks the day that His Majesty King Maha Vajiralongkorn was crowned.
The previous Coronation Day was May 5, when the late King Rama IX was enthroned.
Assistant government spokesman Athisit Chaiyanuwat said the change would give Thailand a total of 19 official holidays.
This includes the recently announced new holiday of June 3, which is the birthday of Her Majesty Queen Suthida.