According to Ken Thornton in his book "Thorntons in North Carolina", Thomas was a Captain of Militia in the British army. He joined under General Cunningham. Because of his being an officer, he was subject to the death penalty during the Revolutionary War. Thomas and his brother John served in the militia from June 14, 1780 under Captain Henry Rudolph and Colonel John Cotton in the Stevens Creek militia. Thomas was in the Battle of Kings Mountain. From April 10, 1781 until May 5, 1781, he served under Lt. Colonel Baly Cheney in the 96th Brigade. On August 23, 1781 , he was at Dorchester under Cotton. He served as lietenant under Cheney in the 96th Brigade and as Captain from April 4, 1782 under December, 1782 under Colonel Thomas Pearson of the Little River militia. He took his three sons to Nova Scotia when they fled Charleston, South Carolina on December 13, 1782, during the evacuation of that city. When Thomas died soon after arriving in Nova Scotia, he left the care of his two youngest sons, Abraham and Eli, in the care of his fellow soldier, Rueben Lively. They would have been cared for by Mr. Lively until the boys were 21 years old and would have been taught a trade. All three of Thomas' sons : Thomas, Abraham and Eli were given 250 acres of land in Nova Scotia as their inheritance.        

The following is a biography of Thomas from the book "Biographical Sketches of Loyalists of the American Revolution" (1984) by Gregory Palmer:

Thornton, Thomas, of South Carolina.  A native of America, Thornton settled at Ninety Six, where he had 150 acres, twenty cleared.  He served at first in the British militia under General Cunningham, and again after the reduction of Charleston in 1780.  Thornton moved to Charleston with his family during the evacuation of Ninety Six, and then traveled to Halifax with his children following the death of his wife.  He died at Halifax soon after his arrival.  Thornton's eldest son, Thomas, filed the claim (he was then 21).  Thomas Jr. went to Rawdon, Nova Scotia with his two infant brothers, who were in the care of Reuben Lively.  His father had commanded a company in the regiment of militia by Colonel Thomas Pearson. Thomas Thornton Jr. estimated his loss at 116 Sterling, and received 50 Sterling.  

Thomas (1735-1783) and Elizabeth were listed as the parents of Thomas (1762-1834) when he remarried in Montgomery County, Ohio in 1813.