The following are the official holidays for Thailand during 2015:

Thursday 1st January: New YearтАЩs Day
Wednesday 4th March: Makha Bucha Day
Monday 6th April: Chakri Day
Monday 13th-Wednesday 15th April: Songkran Festival
Friday 1st May: National Labour Day
Tuesday 5th May: Coronation Day
Wednesday 13th May: Royal Ploughing Ceremony *
Monday 1st June: Wisakha Bucha Day
Thursday 30th July: Asanha Bucha Day
Friday 31st July: Khao Phansa
Wednesday 12th August: H.M. the QueenтАЩs Birthday
Friday 23rd October: Chulalongkorn Day
Saturday 5th December: H.M. the KingтАЩs Birthday
Monday 7th December: Substitution Day for H.M. the KingтАЩs Birthday
Thursday 10th December: Constitution Day
Thursday 31st December: New YearтАЩs Eve

* Holiday only for government workers