Thomas Davies was included in the Navy List of Medical Officers in 1814 
Thomas Davies was employed as Surgeon-Superintendent on three convict ship voyages to Australia :
Medway in 1821. The Medway departed England on 13 November 1820 and arrived in Van Diemen's Land on 13 March 1821. No Medical Journal available.
Henry in 1823. The Henry departed London 28th April 1823 and arrived in Port Jackson 26th August 1823.
Thomas Davies kept a Medical Journal from 13th March 1823 to 29 August 1823....... the unusually healthy state of the Guard and Convicts on the Henry may have in some measure depended on the strict attention paid in every part of the ship; a constant ventilation by windsails and keeping fires lighted in the prison daily; at intervals admitting as many on deck at a time as possible; employing them in various ways conducive to health; hammocks most days on deck; special care taken in their use of the cold bath and most particularly their body linen
Asia (111) in 1825. The Asia departed Portsmouth on 5th January 1825 and arrived in Port Jackson on 29 April 1825.
He kept a Medical Journal from 3 October 1824 to 6 May 1825. There were no cases of scurvy on this voyage and the surgeon was pleased to report that there were no cases of illness when the vessel entered Port Jackson........ It may not excite surprise that my anxiety to prolong the existence of men so circumstanced has been great and continued and I beg to remark that in every individual requiring even a purgative and the facility with which the greater number were restored to their former condition, may be conclusive as to the slight tendency of their indisposition to danger. In conclusion I had the satisfaction of discharging my charges in the Colony perfectly healthy.
Notes and Links
The following may be the same man as above:
Thomas Davies was appointed Surgeon to the Hospital ship Astraea at Falmouth on 20 April 1832. 
Thomas Davies M.D., Assistant Physician to the London Hospital, and Lecturer on Medicine