King Bhumibol's Birthday, celebrated on the 5th of December, is a national holiday in Thailand. It commemorates the birth of the late King Bhumibol Adulyadej, who reigned over the kingdom from 1946 until his death in 2016. The day is also known as 'Father's Day' as the monarch was regarded as the father of the nation.

This special day is marked by numerous cultural and traditional ceremonies across the country. People usually start the day by giving alms to monks. Important landmarks and buildings, including the Grand Palace in Bangkok, are decorated in marigold, which was reportedly the King's favorite color. Particularly notable is the ceremony where the Thai people gather to pay respects and light candles at the statue of King Bhumibol in Bangkok.

King Bhumibol’s Birthday serves as a reflection of the late King's life and achievements. Known as Rama IX, he was the longest-reigning Thai monarch and a much-loved figure who worked tirelessly for the benefit of his people. His work in the fields of development and agriculture amongst others has left an indelible legacy in the country. Amid the celebrations, people also participate in charitable activities, as a tribute to the benevolent work of their late king.