The 23-year-old, of Hawick, was named originally as the squad’s 13th player for the Japanese games but she got on in their final group match against Kenya and swiftly scored a try at her first-ever Olympics.
She crossed the line late in the game after collecting a pass from Abbie Brown for GB’s concluding try in a 31-0 victory over Kenya, setting them up for a place in the quarter-finals.
Thomson, a former captain of the full Scottish women’s squad, normally plays centre for the XVs, and she was joined in the Japanese capital by her fellow Scotland centre Hannah Smith, who also got in among the tries.
The GB women were desperately disappointed to miss out on a medal, going down 21-12 in the third-place match to Fiji.
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They had fought back in the later stages of the semi-final against France but went down 26-19 to the eventual runners-up, who lost 26-12 to New Zealand in the gold medal decider.
Earlier, the GB women had opened their account in pool A with a 14-12 victory against Russia and a 26-21 defeat by New Zealand before their victory over Kenya.
They then saw off the USA in the quarter-finals by a scoreline of 21-12.
GB Rugby Sevens tweeted it “couldn't be any prouder of this truly inspirational team”, as well as extending thanks to the National Lottery UK for enabling the men’s and women’s squads to go to Tokyo.