Hi Karen
He is not listed in either the 1827 Army List or the one for 1850. You will have to find one just after Waterloo, say 1816 to 1820. If you google “army list” you might find one on CD, if you cannot get a lookup. There is an almost complete set in Kew if you can get there. Anyone at Waterloo has a gothic W against their name in all subsequent Army Lists.
I did manage to find him in the London Gazette online search:
= Feb 1794 -
http://www.london-gazette.co.uk/issues/13625/pages/160Lt Joseph Thompson to be Captain-Lt in 40th Foot
= May 1802 -
http://www.london-gazette.co.uk/issues/15478/pages/468Captain Joseph Thomson to be Major in 40th Foot
= July 1803 -
http://www.london-gazette.co.uk/issues/15602/pages/874A Reserve battalion of Infantry, The Honorable,G.
Chetwynd Stapleton, to be Colonel, with temporary
Rank in the Army, vice Peter, whose
Appointment does not take Place.
Brevet Major Joseph Thompson, from the 40th Foot, to be Major.
Note the two spellings; and “vice” means replacing.
The problem is that I could not find him after 1803. Neither can I find out what the Reserve Battalion was renamed to. A lookup in the Waterloo medal roll and for the MGS (Military General Service) medal - awarded for service either in the Peninsular or against the Americans in 1812-1815 - would also help.
From the 1781 Army List there is a Lt Joseph Thompson in the 40th Foot (in America at the time). He obtained his rank in April of that year.
There is also a Captain John Thompson in the 69th Foot, with rank effective 9 Oct 1775.
The "Hon G" is probably Granville who later became a Major General
Ken