Architect and engineer. Thomson was born in Edinburgh, where he trained. He joined Dundee Corporation and was involved in the implementation of the City's Improvement Act of 1871. In 1906, he was appointed City Architect and was responsible for various public buildings in the city, most notably the Caird and Marryat Halls (gifted by James Caird, and his sister Mrs Marryat), Blackness Library (1909), Coldside Library (1909) and Ward Road Museum (1911). The libraries were designed by his son Frank Thomson. In 1910, he put forward an visionary 50-year plan for the city, intended to make Dundee the Venice of the North, which included a new civic centre, widening and realigning streets to open up new vistas and piazzas in the city centre, and a road bridge over the River Tay making use of the foundations of the old rail bridge. He also proposed a ring-road (the Kingsway), a concept far ahead of it time. In 1922, Thomson was also appointed Housing Director and he had been responsible for implementing the first large-scale municipal housing schemes in Scotland.
Thomson was also the first from a Scottish town to be elected President of the Institution of Municipal and County Engineers.