The central Bangkok Sanam Luang royal cremation ground was turned into a sea of light as tens of thousands of people held candles and sang the royal anthem. Similar ceremonies were held simultaneously across the kingdom.
King Bhumibol acceded to the throne at the age of 18 when the Thai monarchy's future was in doubt. Acting behind the scenes, with few legal powers, he has trodden a wary path with successive military rulers to rebuild the institution's prestige.
While the king presided over a ceremony in the morning honouring his royal ancestors, the first of some 30,000 convicts to see early freedom under a royal pardon stepped through prison gates into the arms of relatives.