0132 GMT September 24, 2018
David Mead scored a hat-trick as the rampant host ran in 10 tries, while Regan Grace claimed Wales' only try with the last play of the game, BBC reported.
Only the winner of Pool C, which also features Ireland, will qualify for the quarterfinals.
"I didn't think we performed well in any aspect. It's been a very harsh lesson," said coach John Kear.
Wales has not won at the World Cup since it beat PNG in 2000.
Australia beat England 18-4 in the tournament opener on Friday, while New Zealand overcame Samoa 38-8 in Auckland on Saturday and Fiji beat the United States 58-12 in Townsville, Australia.
In 29C heat and roared on by the passionate fans of the only nation in the world for whom rugby league is the national sport, PNG scored two early tries through the impressive Mead.
Nene Macdonald also went over and Rhyse Martin added the game's first extras.
The game was stopped briefly when Wales' Ben Evans claimed he was bitten on a finger in a tackle by Wellington Albert. Referee Ben Cummins put the allegation on report, to be investigated after the match.
Kato Ottio went clear before Garry Lo sent Albert through following a cross-field run, Minoga also struck and Rhyse Martin went over twice after the break.
Olam gathered Martin's grubber to cross before Mead completed his hat-trick, and Paul Aiton capped a dominant display before Courtney Davies converted Grace's consolation for Wales.
Kear said, "The southern hemisphere fellas really do carry the ball very aggressively and, if you don't stand up to that, you end up getting rolled and losing field position.
"We just never got any opportunity to attack. I've got to compliment them, but people will now probably see how to handle them. We didn't do it very well."
Papua New Guinea plays Ireland in Port Moresby on November 5 (0600 GMT), while Wales faces Fiji –which is in Group D – in Townsville (0830).