His father was an Irish immigrant, and fought with the Continental Army, was wounded and received a pension.

Thomas received a common school education and fought with the U.S. Army the War of 1812.

In 1819 he moved to Boonville, Indiana, where he taught school and studied law.

He ran unsuccessfully for lieutenant governor in 1839 and was appointed as a Democrat to the U.S. Senate to fill the vacancy caused by the resignation of Lewis Cass, serving in the 30th Congress from June 8, 1848 until March 3, 1849.

He moved to Niles, Michigan in 1851 and served as probate judge of Berrien County from 1852 to 1855.