The Welsh centre cum wing, whom also played full back and fly-half, was the youngest player selected for the 1950 Lions tour to New Zealand and Australia.
He played in 15 games on his first Lions tour, scoring 96 points, and played in two Tests defeats in New Zealand and one victory in Australia.
His first game in Lions colours saw him land a record-breaking six penalties against a Combined Nelson-Marlborough-Golden Bay-Motueka XV, while a near length-of-the-field try took his personal tally to 21 points - the most by a Lion at that time.
He repeated the 21-point haul in his first game in Australia, when the Lions beat New South Wales Country 47-3. He kicked six conversions, scored two tries and added a penalty for a record that stood until 1959 when lightning struck for the second time for Thomas against the Combined XV.
A broken leg in a pre-season trial match in 1954 had cost Thomas any chance of challenging for a place on the 1955 Lions tour to South Africa, but he was still in good enough form in the 1958/59 season to be chosen as the one 30+ player in the tour party - and the only survivor from 1950.
This time he played 17 times in New Zealand and Australia, scoring 56 points and picking up another Test cap against the All Blacks.
When the Lions arrived in Blenheim, to face the same Combined Nelson-Marlborough-Golden Bay-Motueka XV that Thomas had put to the sword nine years earlier, they gave the Newport all-rounder the honour of captaining the side from full back.
Having seen Ireland's David Hewitt equal his record of 21 points in a match twice on the trip, against Queensland and Hawke's Bay, he reasserted himself by scoring 25 points. He converted eight of the Lions' 13 tries and also kicked three penalties in a record 64-5 victory. Those eight conversions surpassed the seven kicked by Lewis Jones in the end of tour win over Ceylon in 1950 to give him another record.
His points and conversion records were finally beaten by England's Alan Old in South Africa in 1974, when Old scored 36 points, including 15 conversions, against South West Districts in a massive 97-0 win for the Lions.
Outside of his achievements with the Lions, Thomas won two Grand Slams, two Triple Crowns and three outright Five Nations titles with Wales.
Thomas won 27 caps for his country between 1949 and 1959, playing at wing, centre and fly-half.
He famously scored the try that ended Wales' 39-year wait for an eighth Triple Crown against Ireland in Belfast on March 11, 1950. With the game tired at 3-3 with the Ravenhill clock showing a mere three minutes left to play, Thomas dived over in the left corner for a match-winning score as Wales completed stage three of their first Grand Slam since 1911.