Thomson was clerk-in-charge of the office of the Melbourne and Hobson's Bay railway during its construction.

[2] After two years in Nelson, he had a short experience on the Otago gold fields, and in 1865 settled in Christchurch, where he was employed by the jewellers Coates and Co., the company of his father in law.

Thomson moved that Wilson be elected as the first mayor of Christchurch, and Tombs seconded the motion.

[6][5] At the end of 1877, Thomson stood for Mayor of Christchurch against the incumbent, James Gapes.

Gapes declared that he would not have wanted to oppose a city councillor standing for the office of mayor, but that he stood to clear up his reputation, as unwarranted accusations had been made against him.

[10] Thomson stood for re-election against the senior councillor Charles Thomas Ick.

[1] Westby Perceval, Aaron Ayers, Thomson and Eden George contested the Christchurch South electorate in the 1887 election.