# Franco-Siamese Treaty of 1687
The Franco-Siamese Treaty of 1687 (สนธิสัญญาไทย–ฝรั่งเศส พ.ศ. 2230) was a trade and stationing agreement signed between the kingdom of Siam under King Narai and the France of Louis XIV, following the arrival of a large French embassy and military expedition in September 1687. It allowed French troops to occupy the fortresses of Bangkok and Mergui. The arrangement lasted barely a year: the [Siamese revolution of 1688](https://www.edgepedia.org/siamese-revolution-of-1688) overthrew Narai's dynasty, executed his favorite [Constantine Phaulkon](https://www.edgepedia.org/constantine-phaulkon), and forced the French garrison out of the country.
| Key fact | Detail |
|---|---|
| Parties | Siam under King Narai; France under Louis XIV[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) |
| French envoys | Simon de la Loubere (politics and religion) and Claude Ceberet du Boullay (trade); troops under General Desfarges[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) • [2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)) |
| Expedition | Left Brest 1 March 1687; arrived at the Chao Phraya mouth 27 September 1687[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) • [2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)) |
| Forces | 1,361 passengers including 636 soldiers; only 492 soldiers survived the voyage[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) • [2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)) |
| Treaty terms | Trade treaty signed in November or December 1687; Bangkok ceded as a French garrison, Mergui occupied[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) • [3](https://thesiamsociety.org/wp-content/uploads/1992/03/JSS_080_1h_FrancoSiameseRelationsIn17thCentury.pdf) |
| Outcome | Reversed by the 1688 revolution; French troops withdrew and French contact with Siam ended for about 170 years[4](https://thesiamsociety.org/wp-content/uploads/1994/03/JSS_082_0e_Love_MakingOfOrientalDespot.pdf) • [5](https://www.kci.go.kr/kciportal/ci/sereArticleSearch/ciSereArtiView.kci?sereArticleSearchBean.artiId=ART001483724) |
## Background and causes
Diplomatic contact between Siam and France began in 1685, when Chevalier de Chaumont, envoy of [Louis XIV](https://www.edgepedia.org/louis-xiv), traveled to Ayutthaya in the reign of King Narai[6](https://th.diplomatie.gouv.fr/th/relations-bilaterales/relations-bilaterales-france-thailande). Two pressures pushed the two courts together. On the Siamese side, [Narai](https://www.edgepedia.org/narai) sought an alliance with France because he felt threatened by Dutch commercial interests, and hoped to balance Dutch and English power in the region[7](https://www.jstage.jst.go.jp/article/sea1971/1975/5/1975_5_54/_article) • [5](https://www.kci.go.kr/kciportal/ci/sereArticleSearch/ciSereArtiView.kci?sereArticleSearchBean.artiId=ART001483724). On the French side, the Missions Etrangeres de Paris, locked in conflict with priests under the Portuguese Padroado system, sought the backing of Louis XIV's court; in 1684 Bishop Benigne Vachet drafted a memorandum explaining why the king should engage with Siam, which helped bring about Chaumont's embassy of 1685[8](https://so05.tci-thaijo.org/index.php/huru/article/view/27853).
The exchange continued. Louis XIV then appointed a second embassy to negotiate religion and trade with the Siamese court, led by Simon de la Loubere and Claude Ceberet du Boullay[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14). One study of the period argues that the embassy's real goal was probably to establish a protectorate over Siam, using the soldiers sent with the envoys as an initial holding force, rather than the small bodyguard the Siamese king had originally requested[4](https://thesiamsociety.org/wp-content/uploads/1994/03/JSS_082_0e_Love_MakingOfOrientalDespot.pdf).
## Course of events
The expedition assembled at Brest and departed on 1 March 1687[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) • [2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)). It carried 1,361 passengers, including 636 soldiers destined to garrison the fortresses of Bangkok and Mergui, and twelve Jesuits, some of them mathematicians sent to establish observatories at Ayutthaya and Lopburi[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) • [3](https://thesiamsociety.org/wp-content/uploads/1992/03/JSS_080_1h_FrancoSiameseRelationsIn17thCentury.pdf). The voyage was deadly: the historian Charnvit Kasetsiri puts the survivors at 492 of the 636 soldiers[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) • [2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)).
The fleet reached the mouth of the [Chao Phraya River](https://www.edgepedia.org/chao-phraya-river) on 27 September 1687, after a voyage of six months and twenty-seven days[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) • [2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)). General Desfarges commanded the troops, Loubere handled political and religious interests, and Ceberet the trade treaty[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14). Father Guy Tachard went ahead and met Constantine Phaulkon, the Greek favorite of King Narai, before [Kosa Pan](https://www.edgepedia.org/kosa-pan) and his colleagues could advise against the cession of Bangkok and Mergui; Phaulkon then convinced Narai and his Council to place the two strongholds under French "protection"[3](https://thesiamsociety.org/wp-content/uploads/1992/03/JSS_080_1h_FrancoSiameseRelationsIn17thCentury.pdf). Phra [Phetracha](https://www.edgepedia.org/phetracha), chief of the elephantry, was the only member of the Council to speak against the proposal, which the king approved[3](https://thesiamsociety.org/wp-content/uploads/1992/03/JSS_080_1h_FrancoSiameseRelationsIn17thCentury.pdf).
The French then occupied Bangkok and Mergui amid the discontent of senior ministers[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14).
Other accounts date the concluded treaty to 11 December 1687[2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)) • [9](https://www.historyatlas.com/events/the-king-is-forced-to-accept-their-occupat/). Three copies of the treaty, in Portuguese, Thai, and French, were kept in the Paris archives[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14); a Thai epigraphy database also preserves the treaty text under a lunar date of the first month, eighth day of the waxing moon, B.E. 2231, year Tho[10](https://db.sac.or.th/inscriptions/inscribe/detail/1204).
## Consequences and political influence
The treaty gave France what its envoys had sailed for: a trade agreement and a military foothold at Bangkok[4](https://thesiamsociety.org/wp-content/uploads/1994/03/JSS_082_0e_Love_MakingOfOrientalDespot.pdf). The gains were short-lived. The revolution of 1688 reversed every grant the treaty had made: it toppled Narai's dynasty, executed Constantine Phaulkon, and forced the French troops out of the country[4](https://thesiamsociety.org/wp-content/uploads/1994/03/JSS_082_0e_Love_MakingOfOrientalDespot.pdf) • [5](https://www.kci.go.kr/kciportal/ci/sereArticleSearch/ciSereArtiView.kci?sereArticleSearchBean.artiId=ART001483724). Formal diplomatic relations between the two countries were only re-established by a treaty of friendship and commerce much later, whose 170th anniversary falls in 2026[6](https://th.diplomatie.gouv.fr/th/relations-bilaterales/relations-bilaterales-france-thailande).
## Historians' assessment
Historians read the treaty as the high point of a short-lived alignment. Franco-Siamese relations in the seventeenth century reached their peak in September 1687, when the French squadron arrived in the Gulf of Siam to station troops in Bangkok[7](https://www.jstage.jst.go.jp/article/sea1971/1975/5/1975_5_54/_article). The 1688 palace revolution that undid it is seen as the expression of the opposition of the Siamese conservative bureaucracy against King Narai's pro-European foreign policy[11](https://www.kci.go.kr/kciportal/landing/article.kci?arti_id=ART001665323), and Phetracha became the heart of a nationalist anti-French movement joined by Kromluang Yothathep, Narai's daughter[3](https://thesiamsociety.org/wp-content/uploads/1992/03/JSS_080_1h_FrancoSiameseRelationsIn17thCentury.pdf). On the French side, the episode is assessed as an attempt at a protectorate that overreached what the Siamese court had asked for[4](https://thesiamsociety.org/wp-content/uploads/1994/03/JSS_082_0e_Love_MakingOfOrientalDespot.pdf).
Two details of the record remain unsettled between serious accounts: the treaty's signing date is given as 11 November 1687 in one narrative[1](https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14) and as 11 December 1687 in two others[2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)) • [9](https://www.historyatlas.com/events/the-king-is-forced-to-accept-their-occupat/), and the squadron is described as five vessels at departure[3](https://thesiamsociety.org/wp-content/uploads/1992/03/JSS_080_1h_FrancoSiameseRelationsIn17thCentury.pdf) • [2](http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)) but six warships on arrival in the Gulf of Siam[7](https://www.jstage.jst.go.jp/article/sea1971/1975/5/1975_5_54/_article).
## References
1. คณะทูตชุดที่สองของพระเจ้าหลุยส์ที่ 14 ในราชสำนักสยาม: https://www.catholichaab.com/main/index.php/2015-09-22-02-53-59/2018-10-26-03-35-52/1787-14
2. Frankrikes andra ambassad till Siam (1687): http://thailandshistoria.se/artiklar/10/14/ayutthaya/constantine-phaulkon/frankrikes-andra-ambassad-till-siam-(1687)
3. Aspects of Siamese-French Relations in the 17th Century, Journal of the Siam Society: https://thesiamsociety.org/wp-content/uploads/1992/03/JSS_080_1h_FrancoSiameseRelationsIn17thCentury.pdf
4. The Making of an Oriental Despot (The Seventeenth Century), Journal of the Siam Society: https://thesiamsociety.org/wp-content/uploads/1994/03/JSS_082_0e_Love_MakingOfOrientalDespot.pdf
5. 아유타야시대 태국과 프랑스와의 관계(1662-1688): https://www.kci.go.kr/kciportal/ci/sereArticleSearch/ciSereArtiView.kci?sereArticleSearchBean.artiId=ART001483724
6. ความสัมพันธ์ทวิภาคีฝรั่งเศส-ไทย, French Ministry for Europe and Foreign Affairs: https://th.diplomatie.gouv.fr/th/relations-bilaterales/relations-bilaterales-france-thailande
7. The 'Révolution' of 1688 in Thailand, Southeast Asian Studies: https://www.jstage.jst.go.jp/article/sea1971/1975/5/1975_5_54/_article
8. คณะมิสซังต่างประเทศแห่งกรุงปารีสกับความสัมพันธ์ระหว่างฝรั่งเศส-สยาม ค.ศ. 1667-1685: https://so05.tci-thaijo.org/index.php/huru/article/view/27853
9. 1687 CE: the King is forced to accept their occupation, History Atlas: https://www.historyatlas.com/events/the-king-is-forced-to-accept-their-occupat/
10. ฐานข้อมูลจารึกในประเทศไทย: สัญญาไทย-ฝรั่งเศส ครั้งสมเด็จพระนารายณ์ฯ: https://db.sac.or.th/inscriptions/inscribe/detail/1204
11. The Siamese Reactions to the French Influences and the 1688 Palace Revolution: https://www.kci.go.kr/kciportal/landing/article.kci?arti_id=ART001665323
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*Topic: Encyclopedia › Society and history › History and archaeology › Asian history › Southeast Asia › Siam (1238 to 1767)*
*Initially written Sep 24, 2026 · Edited: Oct 15, 2026; Oct 25, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license