After finishing his major league career with a .255 average, 106 home runs and 428 RBI, Thomas played for the Nankai Hawks of Nippon Professional Baseball in 1969.

[5] The trade began his five-year tenure as an everyday player: he appeared in 486 games for the Angels, and 258 more for the Boston Red Sox, who acquired him for outfielder Lou Clinton on June 4, 1964.

[2] On December 15, 1965, the Red Sox traded Thomas, Arnold Earley, and a player to be named later (Jay Ritchie) to the Atlanta Braves for Dan Osinski and Bob Sadowski.

[12] After he signed a minor league contract with the St. Louis Cardinals organization for the 1970 season,[13] they assigned him to the Tulsa Oilers of the American Association, where he concluded his 17-year pro playing career at age 34.

He was a key member of the St. Louis organization during the club's run of success during the early to mid-1980s when the Cards, led by manager Whitey Herzog, won NL pennants in 1982, 1985 and 1987 and the 1982 World Series.

He acquired players such as Curt Schilling, Lenny Dykstra and Mitch Williams, who played critical roles in the Phillies' 1993 pennant-winning team, which lost the 1993 World Series to the Toronto Blue Jays.

[19] He played a key role in Boston's signing of free agent outfielders Manny Ramírez in December 2000 and Johnny Damon one year later.

He served the Astros and the Milwaukee Brewers as a scout,[20] and on December 4, 2011, he joined the Baltimore Orioles as a special assistant to Duquette, who was the executive vice president.