[3][4] Whilst playing for Wigan Thomas was selected to go on the 1914 Great Britain Lions tour of Australia and New Zealand, playing as a fullback in the second Test match of the Ashes series against Australia.
[5] However the Barbarians website say that it wasn't him, that instead it was another Gwyn Thomas who also played rugby union for Neath RFC.
[6][7] Whilst playing for Huddersfield Thomas was selected to go on the 1920 Great Britain Lions tour of Australasia.
He was vice-captain, and played at fullback in all three Test matches of the Ashes series.
During the 1921–22 Kangaroo tour Thomas was selected to play for Great Britain at fullback against Australia in all three test matches of the Ashes, which was won by the British.