A native of Pontiac, Michigan, who also lived on military bases in South Carolina and Washington, Thomas eventually settled in Orlando, Florida.

Thomas took on a number of contenders and champions before his first championship; After a win over multiple time world title challenger James Tillis, in 1983, Thomas took Gerrie Coetzee to a draw, who later that year won the WBA heavyweight belt, and defeated the eventual WBC cruiserweight champion, Alfonso Ratliff By 1984, with a record of 24–0–1, he would get his first world title shot against reigning WBC heavyweight champion Tim Witherspoon in August 1984, in Las Vegas, Nevada.

Thomas came back and reeled off three ko wins before setting up a May 1987 challenge to WBC and WBA Heavyweight champion Mike Tyson.

Although Thomas allegedly took the fight with a serious shoulder injury,[4] he enjoyed success outjabbing Tyson.

After a long break for a torn glove, action resumed in the 6th round in which Tyson had regained his energy and Tyson knocked Thomas out with a brutal fifteen punch salvo, knocking the extremely durable Thomas down for the first and only time in his career.

Thomas attempted one final comeback in 1992, winning twelve fights before outpointing Craig Payne.