 On 7 October 1950, Kelly was called into the Northern Irish team for a match against England and manager Sid Cann promoted Thomas to the first-team for a match against Birmingham City.At a month before his 18th birthday, Thomas thus became Southampton's youngest-ever first-team goalkeeper, until the debut of Bob Charles in 1959.Although the match was lost 2–0, Thomas was not deemed to be at fault for either of the goals.