The 22-year-old lock's deal to the end of 2027 follows hot on the heels of the Dolphins' acquisition of North Queensland forward Kulikefu Finefeuiaki, also on a three-year deal, from next season.
Plath, the son of four-time premiership winning Brisbane utility John Plath, was already on the Dolphins' books until 2026 but has agreed an upgraded contract with an extra year tagged on the end.
Fox Sports statistics show Plath has made 128 tackles in four games this season with none missed.
It is a remarkable record for such a young player and testament to his technique and attitude.
Plath provides a template for how the third-placed Dolphins play football.
He works hard at training, he competes hard on the field and he shows his skill.
Those tenants are the 'Holy Trinity' of the Bennett ethos.
It was no surprise when Bennett singled Plath out in front of his teammates for praise at a training session in the pre-season: the youngster had gone the extra mile in the effort areas and one-percenters.
"I like to pride myself on giving my best each week and not letting my mates down," Plath said after Dolphins training on Thursday.
"I am super-proud to be a Dolphin, and to have my future locked down means everything to me.
"I am excited for the next couple of years and to go on the journey with this good group of blokes.
"I am proud of how far I have come but I have only played six games and don't want to get too far ahead of myself. I am glad the club has put faith in me."
Plath can play in the halves as well and provides utility value, but he has found a home at lock - a position vacated when Queensland forward Tom Gilbert sustained a long-term knee injury in pre-season.
"Gilbo and I are good mates. I have so much respect for him," Plath said.
"I have learned so much from him already and have been leaning on him a lot."
While he never saw his father play in the 1990s, Plath has embraced his legacy.
"It is all about the small things with Dad," he said.
"You don't have to be the best player in the team but just try and do your best in your role and be a good person."
Plath was at the Broncos on a train-and-trial deal early last year before the Dolphins swooped for his signature.
"I wouldn't say I left the Broncos. I was barely there," Plath said.
His signing, along with that of Finefeuiaki, will set the Dolphins up for life beyond Bennett when the coach hands over to his assistant Kristian Woolf at the end of the season.
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