The 'Ikale Tahi maintained their recent dominance over Manu Samoa with a 28-18 victory in the Pacific Nations Cup but a lack of discipline dominated the thoughts of coach Toutai Kefu post-match.
Tonga led 17-6 at half-time thanks to tries from debutant winger Viliame Lolohea and returning flyer Cooper Vuna on the other flank.
The Kingdom extended their advantage to 28-6 when Penikolo Latu combined defence with attack to score a stunning solo try midway through the second half but a lopsided penalty count ultimately caught up with the 'Ikale Tahi as Sosefo Sakalia, Paula Ngauamo and Sitiveni Mafi were sent to the sin bin in the final quarter of an hour, allowing Samoa to score two consolation tries.
Toutai Kefu said the team's high penalty count is a concern.
"I think once we get under a little bit of pressure either from the game or from the referee, in terms of just back to back penalties, we start to lose a little bit of focus and maybe composure," he said.
"We get frustrated early and I think that's just the way we play, we're a very emotional race of people and that's how we play the game.
"We probably need to look at being more composed during tough times."
The 'Ikale Tahi finished third in the truncated Pacific Nations Cup after losing to Georgia the previous weekend but Toutai Kefu was pleased with the progress shown.
"We pretty much had the same game plan in both games: we wanted to play a quick tempo, we wanted to get a quick recycle of the ball," he said.
"Against the Samoans we felt we had a set-piece advantage so we wanted to be confident going to our set-piece and that seemed to work out well.
"I think that's one of our strengths and we can't hide from that is to just play with that quick tempo and that directness against other teams."
Tonga complete their June series this Saturday against Fiji in Lautoka but Toutai Kefu said the team is dealing with mounting injury concerns after two physical encounters.
"Our lock Joe Tuineau he looks like he may be out, so he's our main lineout organiser," he said.
"Valentino Mapapalangi also has a neck injury - he's unlikely to play (and) we've got a few walking wounded in the backs as well so it's not ideal but that's the nature of the game. As long as we can get a decent team on the field this weekend we'll be right."