Tonga coach Kristian Woolf accepted Keaon Koloamatangi's decision to represent Australia, the forward said, and told him he was grateful for their conversation.
"I spoke to Woolfy and he was very grateful for the conversation I had with him. He was respectful and accepted my decision. I have no regrets," Koloamatangi told AAP.
The 28-year-old, who has played 10 Tests for Tonga, including at the 2022 World Cup in England, switched to Australia for last year's Ashes series.
He was undecided about which country he would represent at this year's World Cup, saying in England last year: "Obviously got to talk to my fiancee about it. She's the king of it all."
His fiancée has since approved his choice to stay with the Kangaroos.
Koloamatangi played 25 minutes off the bench in Australia's 24-22 tournament-opening win over New Zealand and is set to start in the front row against Fiji on Sunday night.
"I just want to experience everything. I was lucky enough to play for Tonga in the last World Cup in England," he told AAP.
"I think if Australia comes calling, it's not something you can turn your back on. It's probably the best team you can make, and it's something I want to look back on, knowing I always dreamt of doing it as a kid."
He said representing Australia also mattered because his father is Tongan and his mother is Australian.
"I played for Tonga, I've play Origin (for NSW), and I wanted to play for all the nations that I am eligible for," he said.
"It's something I'm really proud of because I'm just as Australian as I am Tongan. I was born Australian and my dad's Tongan. For me, I just wanted to experience a World Cup in the Australian colours, and I've got a lot of great mates here too."
Koloamatangi said he loved playing for Tonga and was "being blessed to be a part of it" as the small nation played on the big stage.
He is also due to leave South Sydney for the Dragons in 2027.