He also had success in East Asia at the Seoul International Marathon, where he won three times between 2003 and 2006, as well as taking the runner-up spot in 2005. However, he was disqualified after his 2006 win because his doping test at the race was positive for the banned steroid norandrosterone.[5] Thys contested the outcome and a protracted hearing following his competitive ban by Athletics South Africa eventually resulted in his exoneration. Laboratory errors in processing his sample meant the Court of Arbitration for Sport CAS found in his favour.[6][7] In May 2010 the Federal Supreme Court of Switzerland overruled this decision, declaring that the CAS has no jurisdiction over this case.[8] Thys successfully argued to the court that the fact that the same technician had analysed both his positive samples (a breach of the anti-doping rules) had meant that the validity of the tests could not stand. His doping ban was overturned on this basis in 2012 and he was re-instated as the winner of the 2006 Seoul Marathon.[9]
His extensive running career, which began at the age of thirteen, has taken in around forty competitive marathons. He came close to victory at the 2010 Beijing Marathon, but he slowed in the final stages and was runner-up to Siraj Gena.[10]
