King Narai leaned on a French garrison — the 1688 Siamese revolution expelled them

King Narai of Ayutthaya cultivated a French alliance as a counterweight to the Dutch and to factions in his own court. At his Greek minister Constantine Phaulkon's urging, he permitted French troops to garrison fortresses at Mergui and Bangkok. The Chevalier de Forbin, who commanded at Bangkok, later wrote that Phaulkon knew 'what little Dependance there was upon the King's Life, whose weak Constitution was every Day declining,' and sought a foreign power to protect him.

The whole position rested on one man's survival, and a rival noticed the resentment it bred. Phra Phetracha, commander of the elephant corps, 'form'd a Plot to shake off the Yoke' — winning over the Buddhist clergy, the mandarins and, as Forbin recorded, 'the Populace too.' By 1688 anti-foreign feeling, directed at the French and at Phaulkon, was at its height.

When Narai fell gravely ill in March 1688, the alliance flipped within months. Phaulkon was arrested on a charge of treason and executed; Narai died a prisoner within weeks. Phetracha took the throne, and in the siege of Bangkok he invested the French fortress with a large army and cannon for four months, until the French commandant negotiated a withdrawal and sailed for Pondicherry in November.

Forbin's verdict was that the revolution 'in a Moment overturn'd every step that had been taken, in regard to the Alliance with the French.' The counterweight Narai had imported to deter his rivals became the rallying cause that united them against him, and a position built on a single patron evaporated the moment that patron was gone.