The 25-year-old has been limited over the pre-season and started slowly in Collingwood's VFL curtain raiser against the AIS-AFL Academy at the MCG.
But he became more involved in the second and third quarters, finishing with 25 disposals, seven inside-50's and a goal in the Magpies' 15.15 (105) to 9.9 (63) win.
His teammate Andrew Krakouer also returned after an interrupted summer and had an important hit-out.
The goalsneak showed a few signs of being close to his clever best, kicking the first goal of the game and finishing with two majors and 13 disposals.
It didn't all go the way of Thomas' team, however, with the Academy getting off to a quick start and leading by 20 points at quarter-time.
That lead was quickly dashed in the second term when Collingwood kicked seven goals, but the country's most talented group of draft hopefuls showed some fight in the second half.
Geelong Falcons defender Darcy Gardiner was awarded the annual medal for the best under-18s player in the game, narrowly shading key forward Tom Boyd.
Boyd, forecast as an early selection at this year's NAB AFL Draft, took 10 marks (five contested) and kicked one goal in an impressive display.
Fellow forward Ben Lennon also put in a strong effort with his aerial exploits, hauling in six marks and offering a target through half-forward.
The Academy's tour of Europe starts on Saturday, when the squad departs from Melbourne en route to Italy. It will play a game against the European Legion in London, and another combined game in Copenhagen, Denmark, in early April.
BEST
Collingwood VFL: Martin, Hudson, Thomas, Krakouer, Oxley, Kennedy
Australia U18: Gardiner, Boyd, Lennon, Taylor, Perris, Sheed
GOALS
Collingwood VFL: Paine 3, Krakouer 2, Mooney 2, Allan 2, Barden, Kennedy, Martin, Oxley, Rinaldi, Thomas
Australia U18: Salem 2, Boyd, Hourigan, Lennon, Perris, Sheed, Tickner, Tsitas
Follow AFL website reporter Callum Twomey on Twitter at @AFL_CalTwomey.
