Following a successful transition, Thomas was named Best Newcomer in the Premiership after helping Cardiff RFC claim the National Cup, the club's first silverware since 2009.

[6] Thomas made his first start on 7 December 2019, scoring a try and subsequently named Man of the Match.

[10] In 2017, Thomas represented Wales U18 in the Under 19 International Series, featuring in wins over South Africa Schools and England U18.

[11][12] Thomas was selected for Wales U20 for the 2018 Six Nations Under 20s Championship, coming off the bench in the opening match against Scotland, before starting against England at inside centre.

[15] On 7 June 2021 Thomas received his first call up for the senior Wales team for the 2021 Summer Internationals, replacing Callum Sheedy at fly-half in the second half of the match against Canada to win his first cap.