Thomas was 93 years old.
The three-time All-Star spent parts of three seasons with the Mets, having been traded away to the Philadelphia Phillies in 1964.
He spent 17 seasons in Major League Baseball and played the vast majority of his career with the Pittsburgh Pirates.
Thomas also spent time with the Cincinnati Reds, Chicago Cubs, Milwaukee Braves, and Houston Astros, retiring from professional baseball after the 1966 season.
On Twitter, the Mets posted a nice tribute to one of their original stars.
We are deeply saddened to learn of the passing of original Met Frank Thomas. pic.twitter.com/ZNkIrU59ea
— New York Mets (@Mets) January 16, 2023
Over his 17-year career, Thomas had a batting average of .266 and hit a total of 286 home runs.
“The Original” or “Big Donkey”, as he was affectionately known, also had an on-base percentage of .320, a slugging percentage of .454, an OPS of .774, and a WAR of 18.7.
In his first season with the Mets, he hit .266 with 34 home runs.
Thomas would have turned 94 this year on June 11.
The Mets didn’t have much success while Thomas was around, losing over 100 games in each of their first three seasons as a franchise.
But Thomas was a bright spot for a team that had experienced a great deal of misfortune.
His best season in the big leagues came in 1958 with the Pirates.
That year, he had a career-best 35 home runs and 109 RBI.
Thomas played just five games in his final season in 1966 with the Cubs, retiring on May 30 of that season.