He was a delegate to the State constitutional convention in 1838, and the presiding judge of the sixth judicial district court from 1838 until 1844, when he was elected as a Democrat to the United States House of Representatives.
Thompson did not run for reelection in 1850, but instead returned to practicing law. He became an associate justice of the Supreme Court of Pennsylvania from 1857 to 1866, and served as chief justice of that court from 1866 to 1872.
Later career and death
He returned to private practice until his death in Philadelphia on January 28, 1874.