And now, seated alongside fellow electees Tom Glavine and Greg Maddux, it felt official. Thomas had his family in the front row at his introductory news conference, and he beamed with pride and met each question in turn with a humble and enthusiastic answer.
"There's no better feeling," Thomas said of his election. "And like I tell people, it hasn't sunk in yet. We're going to the Mount Rushmore of baseball. We're in that club. I'm just honored and proud."
Thomas, Maddux and Glavine will join managers Bobby Cox, Joe Torre and Tony La Russa in Cooperstown on July 27 for the annual ceremonies. The three managers were elected by the Expansion Era Committee this past December, and the six will make up the largest living class of inductees since 1971.
Thomas, who will turn 47 in May, is the youngest member of the Hall of Fame fraternity, and he said he underwent a startling transformation while waiting to find out if he'd been elected. Thomas joked that he went from "the grumpiest father in the world" to the happiest all in the span of one phone call.
His whole career -- 19 seasons of excellence -- had been stamped with the ultimate seal of approval, and Thomas couldn't have been happier.
The Hall of Fame didn't announce which cap will be on his plaque, but with Thomas, there isn't much mystery. Thomas won both of his American League Most Valuable Player Awards during his 16-season run with the Chicago White Sox, but he said Thursday that he valued his brief tenures with Oakland and Toronto.
"Chicago meant so much to me. Sixteen years in one place," Thomas said of his time spent with the White Sox. "I was hoping to finish there, but I've got to be honest. I spent some time in Oakland, spent some time in Toronto. I met a lot of great people and a lot of great fans there. Honestly, I'm happy that at the end of my career, I got to experience that, because it was eye-opening for me."
Thomas, a .301 career hitter with 521 home runs, was asked Thursday which words he'd like to see associated with his legacy. Appropriately, he chose "consistent" and "driven." Thomas became the only player in MLB history to log seven straight seasons with a .300 average, 20 home runs, 100 RBIs and 100 walks. For that peak, 1991 through '98, Thomas was as consistent as they get.
How did he prepare? Exactly the way you might think. Thomas said that he learned the value of hard work from his father, and he set out to apply it in the weight room and on the field. Thomas, who led the league in walks four times, said he watched video of his stroke every day. But with a quirk.
"Every day I had my own hitting tape, and I would only watch myself doing great. I took that into the game," said Thomas of his routine. "Only good swings. I was big on that. And guys would think I was crazy, but I would come in right before the game and put on my 'Happy Tape.' I'd tell guys, 'This is what I'm going out here to do. This is my Happy Tape. This is the zone I want to be in.' I don't want to watch myself striking out. I want to see myself in a good mood, and that's the frame of mind I kept."
Thomas, for all his skill, could have followed another sporting path.
He originally enrolled at Auburn University to play tight end on the football team, and he said it took a nudge from football coach Pat Dye to point him toward his destiny. Thomas was the Southeastern Conference's Most Valuable Player in baseball as a junior, and he never looked back after that.
Just how strange is that to him? Thomas wasn't drafted in baseball out of high school because of his football prowess, but still his talent wound up coming to the fore. Now, 25 years later, after being a first-round pick, an All-Star and a Hall of Famer, does he think he could've done the same in football?
"No, I couldn't have been a Hall of Fame football player," he said. "I was an average tight end, but I had great hands. Decent blocker, but in the SEC, that's a dime a dozen. I made the right choice."
Thomas, in some ways, may help open the door for other players. The slugger extended his career by playing at designated hitter as he got older, and he's just the second player -- with Paul Molitor -- to be elected to the Hall of Fame despite playing more games as a DH than at any other position.
Thomas, though, bristles at being classified as a designated hitter, and he's not sure that he's really blazing any trails. The five-time All-Star said that he's in the Hall of Fame because of his hitting credentials, and guys like David Ortiz and Edgar Martinez will have to state the same case.
"People keep bringing up that DH thing," said Thomas. "I was an everyday first baseman. I was lucky that my team would say, 'Hey, take a day off.' Because I was on base a lot. I was on three or four times a night with walks and hits, and as a big guy, it's draining. I was thankful that the DH was there so I could go out and do it, but as for going forward, you've still got to get to those pedestals. Five-hundred home runs. Sixteen-hundred or 1,700 RBIs and runs scored. That's why I'm in the Hall of Fame today."
Thomas spoke out against the use of performance-enhancing drugs during his career, and he was asked several times about his perspective on them now that he's a Hall of Famer. True to form, he said that one of the great joys of his career was in knowing that everything he accomplished was clean.
"Going home at night and not worrying about my phone ringing and somebody saying, 'You're linked to this or that,'" he said. "I tell people that I had no stress in my life because of that. I'm proud that my father reared me the way he reared me: To be somebody, and to work your butt off to get there."
There are no shortcuts, said Thomas. That's the lesson he'd like to impart to anybody willing to listen. Thomas will take a few months to reflect on everybody who has helped him reach the summit of his profession, and he'll do his best to distill it into his induction speech in Cooperstown this July.
Judging by the early returns, he'll have no problem doing so with humor. Thomas told an anecdote from early in his career that illustrated his deep reverence for the game and its legends.
"I'm a Georgia kid, so in my household, it was Hank Aaron," Thomas said of the Hall of Fame legend he's most looking forward to meeting. "When my father saw me [during] the first couple years in the big leagues, he said, 'Yeah, you're doing really well. But you're not Hank Aaron.' It was one of those things. I've seen [Hank] at a few events and I've always shied away, because it's Hank Aaron."
Now, Thomas doesn't have to shy away from his idol. He's turned into a legend himself.