After graduating in 1977, Thomaris returned home and joined the coaching staff at Potsdam State a year later.
In 1987, Brian McCutcheon left Elmira to take the top job at Cornell and Thomaris was chosen as his replacement.
In 2013 he was brought on by the Elmira Jackals, a minor professional outfit, as an assistant and worked for the team for three years.
[5] On June 7, 2022, Thomaris was named the first head coach of the Elmira Mammoth of the Federal Prospects Hockey League.
[2] The Mammoth announced on Monday, January 2, 2023 that Thomaris would be taking a leave of absence due to family matters.