Pan was his given name. As foreign minister, he was styled Chaophraya Kosathibodi. He is colloquially called Kosa Pan. He is also known by his former style as a first-class diplomat: Ok-phra Wisut Sunthon. Contemporary French documents recorded his name as Ooc, Pravisoutsonthoon Raatchathoud. His success in diplomatic negotiations earned him the epithet golden-tongued diplomat.
Embassy to France (1686)
To accompany the return of the 1685 French embassy to Siam of Chevalier de Chaumont and François-Timoléon de Choisy, Pan was selected by Constantine Phaulkon, the Prime Counsellor to King Narai, to lead an embassy to France. Pan set out for France in 1686 on two French ships with two other Siamese ambassadors, Ok-luang Kanlaya Ratchamaitri and Ok-khun Si Wisan Wacha, and by the Jesuit Father Guy Tachard. The embassy was bringing a proposal for an eternal alliance between France and Siam. Pan's embassy was met with a rapturous reception and caused a sensation in the courts and society of Europe. The mission landed at Brest, France and journeyed to Versailles, constantly surrounded by crowds of curious onlookers. The embassy stayed in France from June 1686 to March 1687.
1688 Siamese revolution
Upon his return to Siam, Pan was pressured to become a supporter of Petracha's anti-French faction of dissatisfied nobles of whom resented the power that the French held in Siam. The following revolution toppled Narai and ousted the French forces, of which Pan was sent to negotiate with. He became henceforth Petracha's Minister of Foreign Affairs and Trade. Pan was met in Siam in 1690 by the German naturalist Engelbert Kaempfer, who described "pictures of the Royal family of France and European maps" hanging "in the hall of his house": In 1699, Pan and Petracha received a visit from the Jesuit Father Guy Tachard, but the meeting remained purely formal and led to nothing.
Death
Pan was later accused of having affinity to the French and loyalty to his former King, Narai. He was disgraced, had his nose cut off by King Phetracha, and apparently committed suicide on 15 November 1699, according to the Dutch. His duties were taken over by Okya Maha Amath, one of the King's favorites. Nevertheless, he is claimed to be the direct ancestor of King Rama I, founder of the present ruling dynasty of Thailand.
