Thomas attended Langston High School in Hot Springs, Arkansas, before moving on to Bishop College. As a senior, he intercepted 4 passes (2 returned for touchdowns), recovered 3 fumbles and received NAIA All-District 8 honors.
He also participated in the 1971 College All-Star Game against the Baltimore Colts.
Thomas was selected by the Dallas Cowboys in the second round (51st overall) of the 1971 NFL Draft. In training camp he was tried at wide receiver. He had 2 kickoff returns for touchdowns in his rookie season.
One of those returns was a then franchise record 101 yard score against the New York Jets, which still remains the record for a Cowboys rookie, and is tied with Bryan McCann and Amos Marsh for the second-longest play in Cowboys history, behind Alexander Wright's 102-yard kickoff return against the Atlanta Falcons in 1991.
He played only one season with the Cowboys averaging 42.1 yards per kickoff return and was part of the winning team in Super Bowl VI. He was traded on September 5, 1972, to the Green Bay Packers along with punter Ron Widby for a 1973 second round draft choice (#46-Golden Richards).
Thomas continued to return kickoffs and had over 1,000 return yards in 2 seasons with the Green Bay Packers. In 1973, he was used as a wide receiver before being moved back to cornerback. He was waived on August 15, 1974.
In 1974, he signed with the New York Stars of the World Football League and was the starter at strong safety. In October, the team moved to Charlotte and was renamed as the Charlotte Hornets.
In 1975, he signed with the Buffalo Bills and had his only 2 interceptions in the NFL that year. He was released on September 4, 1976. During his NFL career he played 37 games in 4 years, with 1,394 kickoff return yards, 2 interceptions and 2 touchdowns.
In 1977, he signed with the Toronto Argonauts of the Canadian Football League and played there for one season before being released.
In 1978, he signed with the Hamilton Tiger-Cats of the Canadian Football League, playing most of the season before being put on the injured reserve list with a broken hand. He retired on November 14, 1979.