Pierre d'Espagnac was a member of a mission of 14 Jesuit scientists sent to Siam by Louis XIV, under the guidance of Father Guy Tachard.
[2]: 54 D'Espagnac left Brest in March 1687 together with the Loubère–Céberet mission to Siam.
[2] D'Espagnac spoke Portuguese, and served for some time as an interpreter for Constantine Phaulkon.
[1]: 78 The Jesuits were warmly received by the Siamese king Narai, who had great interest in astronomy.
He was captured in Tavoy by the Siamese, together with the Chevalier de Beauregard and four French soldiers, as they were trying to obtain supplies for their ships.