Thomas missed out on the Welsh tour to Argentina and South Africa in the summer of 2004 due to a shoulder injury. He has represented Wales at U19 level and also has Wales A experience.

Thomas joined the Llanelli Scarlets in 2002 on a three year contract from Ebbw Vale. In March 2005, Thomas re-signed his contract with the Scarlets with a three-year extension; later that year he had neck surgery which put him out of action for three months.

The 2006–2007 season saw Thomas excel at domestic level, scoring three tries for his club throughout the year, which earned a call up to the national squad ahead of the two-Test tour of Australia in May 2007. Thomas made the starting line-up for both Tests in Sydney and Brisbane and was later named in Gareth Jenkins's 41-man preliminary Rugby World Cup 2007 summer training squad, though failed to make the final cut.