He was born May 19, 1835 at Fisher’s Grant, Pictou, Nova Scotia, Canada; he later went to work with for his brother, Daniel Foster, in his shipbuilding business in Warren, Bristol County, Rhode Island in the 1850s. In 1857, Thomas and his brother Daniel decided to move to Hawaiʻi to try the shipbuilding business in the Pacific.
Foster met and married Mary Elizabeth Mikahala Robinson, the eldest daughter of James Robinson, the prominent local ship builder in 1861 (they did not have any children.) Foster began Inter-Island Steam Navigation Company. When airplanes came to the Hawaiian Islands, the Inter-Island Navigation Company founded a subsidiary, Inter-Island Airways (Hawaiian Air.)