In 1690, La Chassaigne was commander of Fort Lachine.
He became a midshipman in 1693, a captain in the following year and a naval sub-lieutenant in 1695.
In 1699, he married Marie-Anne, the daughter of Charles le Moyne de Longueuil, Baron de Longueuil.
He served as town major of Montreal in 1710.
In 1711, he was awarded the Cross of Saint-Louis.
He became town major of Quebec City in 1716, king’s lieutenant at Montreal in 1720, governor of Trois-Rivières in 1726 and governor of Montreal in 1730.