After the Treaty of Paris restored peace in 1763, Peynier was given command of the 32-gun frigate Malicieuse, making a voyage of exploration and diplomacy in the Lesser Antilles.

[4] After Grenada, Antoine de Thomassin sailed to the Spanish Coast of South America, visiting the ports of Cumaná and Caracas until June 1765.

Although the British captured part of the convoy, Peynier managed to land troops at the Dutch Cape Colony and sailed on to make his junction with Suffren.

At the Peace of Paris, Suffren was recalled to France, and Thomassin de Peynier kept command of the French fleet in the Indian Ocean until 1786 with the position of squadron leader,[a] which he obtained in 1784.

After the American War of Independence, Peynier went to the United States where he was admitted in the Society of the Cincinnati, receiving his diploma from George Washington.

The political situation there was extremely tense, particularly in 1790: the 212 deputies of the Assembly of Saint-Marc started displaying more and more overt secessionist tendencies.

These deputies, who were all white landowners, went as far as opening the ports of the colonies to foreign trade, which was against the laws of exclusive commerce still in force in the Kingdom of France.

Eighty-five of them left the island aboard the ship Leopard and sailed to France to plead their case with the Constituent Assembly.

On 2 November 1790, Jean-Paul Marat wrote in the L'Ami du peuple: "It is not disputed that the Sieur de Peynier exercised a terrible despotism, that he used violence to disarm the Port-au-Prince National Guard.

[7] In late 1790, White settlers openly accused Governor Peynier and Colonel Mauduit, commander of Port-au-Prince, of protecting men of colour.

[8] Tired and sick, Peynier resigned and handed power over to Philippe François Rouxel de Blanchelande, before embarking for France, where he arrived in early 1791.

The following spring, he accepted command of the Brest Squadron of the French Navy, but after reconsidering, he eventually declined on the advice of the Minister Bertrand-Molleville.

After the fall of the Monarchy and the proclamation of the Republic late in the summer of 1792, Peynier swore before the municipal officer of Orthez, Dutilh, "to be faithful to the Nation and to maintain freedom and equality or die by defending it".

In his testimony to the Orthez District Revolutionary Committee, in a letter date 31 Pluviose An III (9 February 1795), he stated that this arrest stemmed from "oppressive and general measures".