In an otherwise closely contested encounter, Samoa's sloppy ball control inside their own 20-metre zone gave Tonga a free pass to set up camp in attacking territory on a number of occasions, while four of their five tries came directly after Samoan handling errors deep in their own territory.
It contributed to Samoa finishing the match on the wrong end of a lopsided possession count, and post-match coach Matt Parish was fuming at his side's self-capitulation.
"I thought our defence was really good, considering you can't give teams that much ball inside your own 20," Parish said.
"We made too many mistakes inside our own red zone. That was the only difference.
"Unfortunately, individual errors are killing us, killing us."
Giant Warriors winger Ken Maumalo was the main offender for Samoa, coughing up errors in the lead up to Tonga's first three tries, with two dropped kicks which Michael Jennings scooped up for tries, and a sloppy play the ball giving Tonga the ball for Peni Terepo's touchdown midway through the second spell.
Samoa captain Frank Pritchard didn't hold back in his appraisal of Maumalo's performance, while calling for his side to make vast improvements before playing Scotland in Cairns in their final group game.
"Tough night [for Ken], he has got to be better, it's a professional game. You've got to put that to the side, it's an 80-minute game," Pritchard said.
"Kenny is a young lad and he will learn from it, he has got to work hard on the little things.
"We have got to hold the ball, if we want to tackle all night that's going to be hard.
"Those little fundamental things we have got to work on, we have got Scotland next week and it's a must-win."
The result leaves Samoa facing a do-or-die match with Scotland, where the winner is assured of taking the third and final qualifying spot out of Pool B.
Parish said he remained confident his team could get the job done against the Bravehearts, believing people were yet to see the best of his men.
"At [times tonight] I thought we were going to win it, but again we lost our way at times," Parish said.
"I couldn't be happier with the way the guys have trained, the way they are committed to the cause.
"I'm confident going into every game, if we can take what we do on the training park onto the field we will be alright.
"I think I am pretty confident in any game, we have just got to re-group."