He attended the Johns Hopkins University, where he and classmate Edgeworth Smith founded the Johns Hopkins News-Letter in 1896.
Shortly after graduating, Thomson became editor of the Norfolk, Virginia Dispatch, where he worked from 1900–1906. From 1906 to 1941, Thomson served in the position he would hold for most of his life, as publisher of the New Orleans States-Item, then known simply as the Item. The New Orleans States-Item was later merged with the present-day Times-Picayune.
Thomson married Genevieve Champ Clark in 1915, whose father, James Beauchamp Clark, had been a Democratic nominee for president in 1912.
Thomson himself would serve as delegate to the Democratic National Convention in 1920, 1924, and 1944 for the state of Louisiana. He died on September 25, 1959.