Thomas won the world championship at the 2001 World Amateur Boxing Championships in Belfast, Northern Ireland. He was runner-up in 2003 losing to Somjit Jongjohor. Thomas qualified for the 2004 Summer Olympics by ending up in second place at the 2nd AIBA European 2004 Olympic Qualifying Tournament in Warsaw, Poland. In 2007, he lost early against European Champion Georgy Balakshin.