He was appointed by the infant king Louis XIV of France during the regency of Anne of Austria at a time when the colonies were owned by the Company of the American Islands.
His predecessor refused to recognise his appointment, forcefully prevented him from taking office on Saint Christopher Island, and eventually had him arrested and returned to France.
[2] The governor of the English part of the island, Thomas Warner, worked with Poincy to suppress resistance to their authority from the independent-minded settlers, who were suffering from growing competition in the tobacco trade from the Americas.
"[6] On 16 February 1645 the company arranged for a lettre de cachet from the king that ordered Poincy to return to France.
[2] In July 1645 he expelled the intendant general, Clerselier de Leumont, who retired to Guadeloupe, and sent his most troublesome opponents back to France.
[6] Another lettre de cachet from the king dated 18 August 1645 formally demanded that Poincy leave the Antilles.
[6] On 1 September 1645 the company's Assembly of Lords in Paris commanded Robert de Longvilliers, governor of Saint Christopher, to receive Thoisy as the king's lieutenant general for the American islands.
Thoisy then went to the English base at Sandy Point, where Sir Thomas Warner told him that only Poincy's servant could land.
[11] Thoisy and Governor Charles Houël du Petit Pré of Guadeloupe made a plan to overcome Poincy by force.
They dropped their plan when Governor Jacques Dyel du Parquet of Martinique arrived and proposed to kidnap Poincy's two nephews and use them as pawns to force submission.
[11] In November 1646 Houël started a revolt against Thoisy, claiming that his presence on Gaudeloupe deprived him of his rights as governor.
While passing Guadeloupe La Vernade embarked one of Poincy's nephews, Longvilliers, against the promise that Du Parquet would be released.
Thoisy was held prisoner in Saint Christopher, but due to expressions of sympathy for him by the population Poincy embarked him for France at night at the end of April, where he arrived on 17 May 1646.