Born in Edinburgh, Scotland, Thomson was raised in Glasgow where he attended Kelvinside Academy.
[2] He utilised the training link that the university had with Worcester Warriors, and also played for the Scottish Exiles U18s while based in England.
[3] Thomson enrolled in the BT Sport Scottish Rugby Academy in 2016–17 as a Stage 3 player.
[9] Joining the Warringah Rats on Sydney's Northern Beaches,[9] Thomson played in the club's Shute Shield premiership-winning team of 2017.
[12] On 14 September 2020, Thomson makes move to Japan with Toshiba Brave Lupus on the Top League competition ahead of the 2020–21 season.