The announcement under Section 37 of the Financial Institutions Businesses Act BE 2551 (2008), was published on the Royal Gazette website on Friday.
The 18 public holidays are:
January 1: New Year’s Day
February 26: Makha Bucha Day
April 6: Chakri Memorial Day
April 13-15: Songkran Festival
May 3: Substitution for National Labour Day (May 1)
May 4: Coronation Day
May 26: Visakha Bucha Day
June 3: HM the Queen’s Birthday
July 26: Substitution for Asarnha Bucha Day (July 24)
July 28: HM the King’s Birthday
August 12: HM the Queen Mother’s Birthday and National Mother’s Day
October 13: HM the late King Bhumibol Adulyadej Memorial Day
October 25: Substitution for Chulalongkorn Memorial Day (October 23)
December 6: Substitution for HM the late King Bhumibol Adulyadej’s Birthday, National Day and National Father’s Day (December 5)
December 10: Constitution Day
December 31: New Year’s Eve
Financial institutions in Narathiwat, Pattani, Yala, Satun and Songkhla provinces can use Eid ul-Fitr, Eid al-Adha and Chinese New Year’s Day as additional public holidays.
https://www.nationthailand.com/news/30394439