The Swede held a one-stroke lead over American Chris Biggins and Spaniard Juan Postigo Arce after day one at Jumeirah Golf Estates and fought off his nearest rivals with an assured level-par 72 at the Earth Course on Saturday.
Lia, who turns 22 in January, becomes the fourth different champion of the inaugural G4D Tour season, joining four-time winner Kipp Popert, Mike Browne and Tommaso Perrino.
He carded four birdies on a three under par back nine to clinch victory with a three over par total, with Biggins and Canadian Kurtis Barkley in a share of second place at seven over.
“It was very exciting, special today,” said Lia, who was the only player to shoot level par or better across the two days of competition.
“It feels unreal to be here right now.”
Lia began his final round with a birdie on the first for the second day running, but two bogeys and then a double bogey at the ninth saw him turn in 39 with a one-shot advantage over World Number One Popert, Biggins and Brendan Lawlor.
But with players on his tail on the back nine, Lia found his mojo to record three consecutive birdies from the 13th, before he cancelled out a bogey at the par-three 17th with a closing birdie to seal a deserved triumph.
“I definitely felt the pressure,” he said.
“I didn’t look that much at the leaderboard but I had a feeling that it was going to be close. I made a few nice birdies on the back nine and managed to finish strong.”
Lia, who had his father Trond as his caddie for the first time this week, was one of eight leading golfers with a disability taking part in the final event of the inaugural G4D Tour season.
Across the year, seven events have been held on the same course and the same week as DP World Tour tournaments, and Lia says a strong message has been sent to inspire future generations of disability golfers.
“Work hard, keep believing in yourself and maybe we can be on this stage someday,” he said.