Thomson was born in Dudley in Staffordshire, England and moved across the border into Wales as a child when his family settled in the Ruabon area, together with his older brother David. Thomson worked as a timber merchant but later assisted his father, who was the manager of the New British Iron Works situated in the Wynnstay district of Ruabon.
In February 1876, Kenrick organized trial matches to select Welsh players to represent their country in a match against Scotland. The international match was played at Hamilton Crescent, Partick, the home of the West of Scotland Cricket Club on 25 March 1876, with Thomson playing as a central forward in a 2–2–6 formation. The Welsh were well defeated, conceding four goals without reply.
The return match came on 5 March 1877 at the Racecourse Ground, Wrexham, with Thomson playing on the left-wing.
The Scots were again victorious, winning 2–0. In 1877-1878, Thomson, described as "a hard-working forward whose forte was running with the ball but (who) was none too accurate in his shooting", helped reach the first Welsh Cup final on 30 March 1878, losing 1–0 to local rivals Wrexham.
Thomson retired from playing football in 1880, but remained active with Wynnstay cricket club When the iron company went into liquidation in about 1887, Thomson left Ruabon to settle in Cheltenham where he died in 1937.
All three played a prominent role in the foundation of the Football Association of Wales in early 1876, with George being a member of the original committee of the Association.
