| Honorific Prefix: | Mom Luang |
| Office: | His Majesty's Principal Private Secretary |
| Termstart: | 18 September 1969 |
| Termend: | 1 October 1994 |
| Predecessor: | Nikorntewan Devakula |
| Successor: | Peerapong Kasemsri |
| Nationality: | Thai |
| Thawisan Ladawan | |
| Native Name: | ทวีสันต์ ลดาวัลย์ |
| Native Name Lang: | th |
| Birth Name: | Thawisan Ladawan |
| Birth Date: | 26 January 1924 |
| Birth Place: | Bangkok, Thailand |
| Death Place: | Bangkok, Thailand |
| Occupation: | Diplomat |
| Parents: | Bung Ladawan Nueang Bunnag |
| Spouse: | Busba Kitiyakara |
| Children: | Suthawan Sathirathai |
Thawisan Ladawan (Thai: ทวีสันต์ ลดาวัลย์; 26 January 1924 – 7 April 2006) was husband of Busba Kitiyakara (younger sister of Queen Sirikit), a member of King Bhumibol Adulyadej's Privy Council, and for 26 years, Principal Private Secretary to King Bhumibol Adulyadej.
Thawisan attended Vajiravudh College and graduated from the inaugural class of Faculty of Law, Thammasat University in 1938.
After graduated, he worked in the Ministry of Foreign Affairs. He worked in several capitals, including Paris and Brussels, and earned a Diplome d'Etudes Superieures de Droit International Public from Paris University in 1954. He became Deputy Director-General of the Protocol Department before departing in 1968 to serve as Deputy Principal Private Secretary to King Bhumibol. A year later he became King Bhumibol's Principal Private Secretary, and was later appointed to the Privy Council.
Thawisan was the son of Phra Phum Phichai (Mom Ratchawong Bung Ladawan) and Nueang Bunnag. His father was the ruler of Chaiyaphum Province, Lamphun Province, Mae Hong Son Province, and Kamphaeng Phet Province.
Thawisan married Busba Kitiyakara in 1958. They had a daughter, Suthawan Ladawan Sathirathai on 24 September 1958. He divorced her soon afterwards and never remarried. Suthawan married Surakiart Sathirathai.
He died at the age of 82 due to chronic liver disease.[1] [2]