She served as the SNP Business, Innovation and Skills spokesperson in the House of Commons until her resignation of the party whip in September 2015.

[8] She worked in Financial Services for Standard Life and the Royal Bank of Scotland for over 23 years in a variety of senior roles delivering IT and business change.

The firm self-funded research involving 236 senior Scottish business leaders across industry to establish their concerns over Brexit.

[12] In November 2018, Thomson was a co-author of a Momentous Change Ltd report into the prospects for establishing a Scottish Stock Exchange.

[19][20] In September 2015, Thomson was accused by an article in The Sunday Times of having built her buy-to-let property portfolio by buying homes for below-market prices.

[21] In late-September 2015, Police Scotland announced it had launched an inquiry into "alleged irregularities" related to the property transactions which had seen her solicitor struck off.

[22] The same day the SNP issued a statement on behalf of Thomson, announcing that she had decided to withdraw herself from the party whip whilst the investigation was ongoing.

[34] She endorsed Kate Forbes in the 2023 Scottish National Party leadership election,[35] taking over running her campaign after Ivan McKee stepped back.