I think this is the A K mentioned on Alyth War Memorial.

Number :-  Thomson, Alexander K

Medal :-

Service :-   Army

Regiment / ship :-  Black Watch (Royal Highlanders)

Date of death :-   7th August, 1917

Cemetery / Memorial :-  Drumoak New Parish Churchyard, Aberdeenshire

Area of cemetery / memorial :-    203

Family information :-    Son of the late David and Agnes Thomson, Mewhall, Drumoak; husband of Christina Abercrombie Thomson of Oak Cottage, Drumoak.

Extra information :-