Thomas first began swimming at the age of four, when his parents took him to the local pool in an attempt to help him burn off excess energy.[3] As he matured, he showed promise as a competitive swimmer and won several junior competitions but the decision made by the IPC, after a controversy at the 2000 Summer Paralympics, meant a competitive ban on all events for athletes with an intellectual disability. This saw him unable to compete at meets for disabled swimmers.[2] His parents petitioned the Equality and Human Rights Commission, the director of which stated in 2008 that the Thomas' letter was a major factor in seeing the Youth Sports Trust lift the ban for children competing in Britain.[2]
In 2013 Thomas was selected to compete at his first major tournament for Great Britain. He came fifth in the 100m backstroke S14 and sixth in the 200m individual medley SM14.[1] The next year he was selected to represent Wales at the 2014 Commonwealth Games in Scotland. There he competed in the 200m freestyle S14, the first event for swimmers with a learning disability.[4] In the finals Thomas took bronze with a time of 2:01.27, behind Australia's Daniel Fox and England's Thomas Hamer.[4] A month later he was back in the Great Britain team, this time travelling to Eindhoven to take part in the 2014 IPC Swimming European Championships. In Eindhoven Thomas was entered into three events the 100m backstroke, 200m freestyle S14 and the 200m individual medley SM14. He won bronze in the 50m backstroke and silver in the medley and freestyle.[1] A wrist injury ruled Thomas out of the 2015 World Championships in Glasgow.[1]
In 2017, Thomas raised money in order to take part in the 2018 Commonwealth Games.[5]
