Friday, 05 December 2014.
Saturday, 05 December, 2015 (Substitution holiday will likely be Monday, 07 December 2015)
Many Thai people will travel to Hua Hin to celebrate the King’s birthday. Countless more will gather throughout the country to feed monks in the morning.
Note that the Emerald Buddha Temple will be open on December 5-6th, but the Royal Palace will be closed both days, and the Royal Chapel will be closed on the 5th but open on the 6th. See Bureau of the Royal Household for more information (Thai language site).