After being acquired by the expansion New York Mets, he led the team with 34 home runs and 94 RBIs in their first season in 1962.

By the end of his career, Thomas had played every infield and outfield position except shortstop, and his 163 home runs with the Pirates placed him second in team history at the time behind Ralph Kiner.

[1] As a teenager he attended Mount Carmel College seminary in Niagara Falls, Ontario, and he studied for the Roman Catholic priesthood for 4+1⁄2 years before entering pro baseball.

[6] Before the 1959 season, the Pirates traded Thomas, Whammy Douglas, Jim Pendleton, and John Powers to the Cincinnati Redlegs for Smoky Burgess, Harvey Haddix, and Don Hoak.

[7] Due to a shattered nerve in the thumb of his right hand, Thomas home run output fell from 35 to 12 in 1959.

[8] Following the season, he was traded by the Redlegs to the Chicago Cubs for Bill Henry, Lou Jackson, and Lee Walls.

[11][12] Despite the team's historically poor inaugural season, Thomas led the expansion Mets with 34 home runs and 94 RBIs.

[13] On August 7, 1964, the Mets traded Thomas to the Philadelphia Phillies for Wayne Graham, Gary Kroll, and cash.