Navigator, employed by the East India Company from around 1748; surveyed and named the Forrest Strait and Passage near the Tenassarim coast. Published various accounts of his travels in the Far East. That of his ‘Voyage to New Guinea and the Moluccas in the years 1774,1775 and 1776’ (published 1779) was illustrated.
About the diary: Published as A voyage to New Guinea, and the Moluccas, from Balambangan : including an account of Magindano, Sooloo, and other islands : and illustrated with thirty copperplates, performed in the Tartar galley, belonging to the East India Company, during the years 1774, 1775, and 1776 : to which is added, a vocabulary of the Magindano tongue by Captain Thomas Forrest, London : Printed by G. Scott, and sold by J. Robson … J. Donaldson … G. Robinson … and J. Bell, Edinburgh, 1780.
The Philippine Diary Project contains the portions related to the Philippines:
November 19, 1774: sighting Basilan;