Thomson would have joined the Belfast Banking Company around 1908.
In 1911 he is boarding in house 18, Scotch Street, Dungannon, Co. Tyrone. The property may have been a hotel. Thomson is described as a Bank Clerk. He served part of his banking career in Ballymena branch.
On 28th September 1912, a Benjamin Thomson signed the Ulster Covenant at the City Hall, Belfast giving his address as 7 Chadwick Street, Belfast.
Thomson served as a private with the Royal Irish Rifles.