[3] On 13 January 2021, Thomas signed a contract with Huddersfield Town until the end of 2023–24 season with the club having the option of a further year's extension.

[6] In the first Championship game of the 2021–22 season, a 1–1 draw with Derby County on 7 August 2021, Thomas got his first assist, supplying a cross from a free kick which was headed in by Naby Sarr.

[7] On 28 August 2021, he scored his first goal (as well as providing two assists) in a 4–0 home victory against Reading: he took possession of the ball at the halfway line, dribbled into the penalty area and placed a low shot past the goalkeeper.

[14] On 28 September 2021, Thomas was called up into the senior Wales squad for the first time for their 2022 World Cup qualifiers against Czech Republic and Estonia.

[15] He made his international debut for Wales on 8 October 2021 as a second-half substitute in the 2–2 draw against Czech Republic,[16] and completed his first full 90 minutes three days later in the match against Estonia.