Pan (Thai: ปาน) was a Siamese diplomat and minister who led the Second Siamese Embassy to France sent by King Narai in 1686.:262–263 He was preceded to France by the First Siamese Embassy to France, which had been composed of two Siamese ambassadors and Father Bénigne Vachet, who had left Siam for France on January 5, 1684. He was a nephew of King Ekathotsarot and a great grandfather of King Phutthayotfa Chulalok, the founder of the Chakri Dynasty. His brother, Lek (เหล็ก), also held the post of foreign minister before him.
Pan was his given name. In formal language, he is usually called by his noble title Chao Phraya Kosathibodi (เจ้าพระยาโกษาธิบดี; "Lord Minister of World Affairs"), the title for the minister of foreign affairs. He is also referred to by his former title Ok Phra Wisut Sunthon (ออกพระวิสุทธิสุนทร; "Count of Pure Amity"), the title for a first-class diplomat.
In informal language, Pan is usually called Kosa Pan (โกษาปาน; "Foreign Minister Pan").
Due to his successful diplomatic efforts, he also gained the nickname "Honey-tongued Diplomat" (ราชทูตลิ้นทอง Ratcha Thut Lin Thong or นักการทูตลิ้นทอง Nak Kan Thut Lin Thong; both literally mean "Golden-tongue Diplomat"). In Thai language, lin thong (ลิ้นทอง; "golden-tongue") means good at speaking or negotiating.
Embassy to France (1686)
Pan set out for France in 1686, accompanying the return of the 1685 French embassy to Siam of Chevalier de Chaumont and François-Timoléon de Choisy on two French ships. The embassy was bringing a proposal for an eternal alliance between France and Siam. It stayed in France from June 1686 to March 1687. Pan was accompanied by two other Siamese ambassadors, Ok-luang Kanlaya Ratchamaitri and Ok-khun Sisawan Wacha, and by the Jesuit Father Guy Tachard.
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.:64–65
1688 Siamese revolution
Upon his return to Siam, Pan became one of the strongest supporters of Petracha, the ruler who eliminated Narai and ousted the French, and became Petracha's Minister of Foreign Affairs and Trade.
"He is a more comely Person, and of better aspect, than I ever met amongst this black race of mankind... He is also quick of understanding and lively action, for which reasons he was a few years ago sent Ambassador to France, of which Country, its Government, Fortresses and the like, he would often entertain us in his discourses; and the hall of his House, where we had a private audience of him, was hung with the pictures of the Royal Family of France, and European Maps, the rest of his furniture being nothing but Dust and Cobwebs.— Engelbert Kaempfer (1727/1987:38).
In 1700 Pan was disgraced, had his nose cut off by King Petracha, and apparently committed suicide. Nevertheless, he is claimed to be the direct ancestor of King Rama I, founder of the present ruling dynasty of Thailand
- Rajanubhab, D., 2001, Our Wars With the Burmese, Bangkok: White Lotus Co. Ltd., ISBN 9747534584
-  Asia in the Making of Europe, by Donald F. Lach, p. 253
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- ออกพระวิสุทธสุนทร (โกษาปาน) [Ok Phra Wisut Sunthon (Kosa Pan)] (in Thai). Historical Archives of the Archdiocese of Bangkok. 4 October 2012. Retrieved 15 July 2014.
- คำแก้ต่าง-ข้อแก้ตัวของโกษาปาน เรื่องปฏิวัติผลัดแผ่นดิน พ.ศ. ๒๒๓๑ [Explanation or excuse of Kosa Pan on 1688 coup] (in Thai). Historical Archives of the Archdiocese of Bangkok. 24 January 2013. Retrieved 15 July 2014.
- Royal Institute of Thailand (2011). พจนานุกรมคำใหม่ เล่ม 3 ฉบับราชบัณฑิตยสถาน [Royal Institute Dictionary of New Words, Volume 3] (pdf) (in Thai). Bangkok: Royal Institute of Thailand. Retrieved 15 July 2014.
- Gunn, p. 188
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- Smithies 2002, p. 35
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- Quoted in Smithies 2002, p. 180
- Smithies 2002, p. 185
- Smithies 2002, p. 180
- Gunn, Geoffrey C. (2003) First Globalization: The Eurasian Exchange, 1500-1800 Rowman & Littlefield ISBN 0-7425-2662-3
- Smithies, Michael (1999), A Siamese embassy lost in Africa 1686, Silkworm Books, Bangkok, ISBN 974-7100-95-9
- Smithies, Michael (2002), Three military accounts of the 1688 "Revolution" in Siam, Itineria Asiatica, Orchid Press, Bangkok, ISBN 974-524-005-2
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- Fine Arts Department of Thailand (1987). Phra Narai, roi de siam et Louis XIV, Musée de l'Orangerie, 13 juin – 13 juillet 1986 (pdf) (in Thai). Bangkok: Fine Arts Department of Thailand.
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- Manop Thanomsi (1990). Chao Phraya Kosathibodi (Pan) (pdf) (in Thai). Bangkok: Ton-O.