Thomas again represented Canada when he played on Team Canada's under 18 team at the 2017 IIHF World U18 Championships in Slovakia, where Canada placed 5th overall. In the same year, he also represented Canada during the 2017 Ivan Hlinka Memorial Tournament, where he scored 6 points to help Canada win their 21st gold title. After the IceDogs were eliminated from the playoffs, Thomas was selected to play for Team Canada at the 2018 IIHF World U18 Championships. He recorded two points in four games and Canada placed fifth overall in the tournament.