Born in Senghenydd, Glamorgan, Thomas moved to England to join Bristol Rovers as a youth player.
He faced competition for his jersey with England youth goalkeeper Phil Kite before going on loan to three clubs during 1982–83, first Cardiff City, then Tottenham Hotspur and Southend United.
During the 1985–86 season he was part of the Newcastle side that lost a club record away defeat to West Ham United 8–1 a game which saw centre back Alvin Martin hit his only first class hat-trick in English professional football, against a three different goalkeepers.
[1] In 1993, after loan spells to Aston Villa and Crystal Palace, Thomas joined non-league club Cheltenham Town.
He eventually earned the UEFA 'A' Coaching licence, taking a position within the Football Association in the early 1990s as a Regional Development Officer in the Midlands.