Tonga batted first with Nikolasi Moala (14) and Aloisio Pau’u (22) putting on a solid opening partnership of 36.
But good bowling from PNG’s Alei Nao had the pair dismissed.
The rest of the Tongan batters did not put up much of a fight as the next five wickets fell for 18 runs.
Tail ender Lea Tenisi chipped in late in the innings with 12 runs.
Tonga was all bowled out for a measly 83.
Jason Kila was the best of the PNG bowlers picking up 3/10.
PNG chased down the target easily in the 10th over thanks to a fired up Raho Sam (33) and Kipling Doriga (26).
The winning run was hit by Jason Kila with a stroke along the ground to mid-on.
In other matches, Vanuatu beat New Caledonia by 73 runs.