Google Thailand Logo - Father's Day
In Thailand, Father's Day is set as the birthday of the king. December 5 is the birthday of the current king, Bhumibol Adulyadej (Rama IX). Thais celebrate by giving their father or grandfather a Canna flower (Dok put ta ruk sa) which is considered to be a masculine flower. Thai people will wear yellow on this day to show respect for the king. This is because yellow is the Color of the day for Monday, the day on which king Bhumibol Adulyadej was born.
It started being celebrated around the 1980s as part of the campaign by Prime Minister of Thailand Prem Tinsulanonda to promote Thailand's Royal family. Mother's Day is celebrated in the birthday of Queen Sirikit.
via wikipedia