"This is a great day today, to be named team ambassador, because I really care about this team," Thomas said before the White Sox hosted the Seattle Mariners on Tuesday night.
The two-time American League MVP will be folded into the White Sox Speakers Bureau, which includes former players Carlton Fisk, Ron Kittle, Minnie Minoso and Bill "Moose" Skowron.
In simple terms, Thomas will represent the team at community and charity functions, shake hands, sign autographs, talk to the crowd, and in general, turn an event away from the ballpark into a happening since it will have such a recognizable team figure on hand.
"Frank Thomas is one of the greatest offensive players in Major League Baseball history and, without question, one of the greatest players in our franchise's long history," White Sox chairman Jerry Reinsdorf said in a release. "It is with great pleasure that we formally welcome Frank back to the White Sox family."
One sign that the White Sox aren't using "Frank Thomas Day" merely to sell tickets is that it will take place before a Sunday afternoon game against the New York Yankees. A big crowd already was expected that day.
Seems like it would make better business sense to have that kind of celebration one series earlier when the Baltimore Orioles are in town. Not to worry, though. There still are some tickets remaining for Aug. 29.
Thomas retired in February after a 19-year career that included 521 homers and 1,704 RBIs. The two-time AL MVP also finished with a .301 career batting average.
The Big Hurt split his final three seasons between Oakland and Toronto, but is remembered most for his long run with the White Sox.
Thomas left Chicago after the White Sox won the 2005 World Series, becoming upset when the club bought out his option for $3.5 million. He criticized the organization, and general manager Ken Williams responded by calling him "an idiot."
"Time heals all wounds," Thomas said. "It's part of being a great player. You know I spent 16 long years here, and, unfortunately, departures are never nice. You've seen it with some of the greatest players in all sports.
"But eventually I figured I would be back here in some capacity," he added. "It just takes time."
Thomas made his major league debut in 1990 and still owns the White Sox records for homers (448) and RBIs (1,465).
"The best hitter to ever wear this uniform was Frank," manager Ozzie Guillen said.
Thomas' number will be the 10th retired by the White Sox, following 2 (Nellie Fox), 3 (Harold Baines), 4 (Luke Appling), 9 (Minnie Minoso), 11 (Luis Aparicio), 16 (Ted Lyons), 19 (Billy Pierce), 42 (Jackie Robinson) and 72 (Carlton Fisk). Robinson's number is retired by all 30 major league teams.
Thomas is a studio analyst for White Sox pregame and postgame coverage on Comcast SportsNet Chicago.
Doug Padilla covers the White Sox for ESPNChicago.com and ESPN 1000. Information from The Associated Press contributed to this report.