Born in Petsoe Parish in Gloucester County, Virginia, Thruston graduated from William and Mary College at Williamsburg, Virginia. He studied law and moved to Lexington, Kentucky (then a part of Virginia) in 1788. He was admitted to the bar and began the practice of law. He was a member of the Virginia assembly in 1789.

After Kentucky was organized as a State, Thruston was elected clerk of the first Kentucky senate in 1792. He was appointed one of Kentucky’s three commissioners to settle the boundary dispute between the states of Kentucky and Virginia. He also served as a district judge of Kentucky 1791, and as a judge of the circuit court from 1802 to 1803. He was also appointed the United States judge of the court of the Territory of Orleans in 1804, but declined the appointment.

Thruston was elected as a Democratic Republican to the United States Senate and served from March 4, 1805, to December 18, 1809, when he resigned, having been appointed to a judicial position. He was appointed judge of the United States Circuit Court for the District of Columbia and served from January 1810 until his death in Washington, D.C. in 1845. He was intered in the Congressional Cemetery.