Chulalongkorn Day is a National Holiday in Thailand held annually on 23 October unless this is a weekend when the holiday will be observed on the following Monday. If you are visiting Thailand at this time, it is worth noting that all Government offices and banks (except those in shopping malls) will be closed.
The day commemorates King Chulalongkorn (Rama V) who passed away on 23 October 1910. He was the fifth monarch of Siam from the House of Chakri and is considered one of the greatest kings of Siam (now Thailand) as he introduced many social and political reforms that helped to modernise the country, including the abolishment of slavery.
He came to the throne in 1868 when he was only 15 years old and was taught English and western customs by Anna Leonowens. Her memoirs of her time in the Siam royal court was retold in the book, 'Anna and the King of Siam' by Margaret Landon. The book was the basis for the popular Broadway & Westend musical and film, The King and I.