Thomas played in the American League (AL) with the Milwaukee Brewers (1973–76, 1978–83, 1986), Cleveland Indians (1983) and Seattle Mariners (1984–86).

He was a leading home run hitter in the late 1970s and early 1980s, though he hit for a low batting average and frequently struck out.

Thomas had good fielding skills and his throwing arm was strong until shoulder surgery in 1984, after which he became a designated hitter until his retirement in 1986.

His family moved to Columbia, South Carolina where he attended Cardinal Newman High School through his junior year, playing on a state championship basketball team in 1968.

[6] The next year with the Class AA San Antonio Brewers, Thomas led the Texas League in the same two categories, registering 26 home runs and 171 strikeouts in 135 games.

[2] Thomas played in Class AAA with the Spokane Indians for the entire 1977 season, batting .322 with 36 home runs and 114 RBI in 143 games.

[10] After the announcement of the trade, angry Brewers fans flooded the team's switchboard with phone calls criticizing the transaction.

On December 7, 1983, Thomas was traded to the Seattle Mariners alongside Jack Perconte in exchange for Tony Bernazard.

[20] Thomas played in only 35 games for Mariners in 1984, batting just .157 with a home run and 13 RBI before he underwent season-ending rotator cuff surgery in June.

Mariners executives said they tried to trade him away but that there was minimal interest in Thomas because of his age and his limitation to the designated hitter role.

[10] In retirement, Thomas played amateur golf and spent time hunting and carving duck decoys.

[29] Thomas works under a personal services contract with the Brewers to make appearances in the community and welcome visitors to Gorman's Grill at American Family Field.