Papalii has dabbled in the Samoan and Kangaroos camps in the past with four games with Samoa and 11 with the Kangaroos.
The Maroons veteran is the latest Australian eligible player to commit to a Pacific Island nation, joining Panthers duo Jarome Luai and Brian To’o.
“As an older player, I feel like it’s a movement I just don’t want to be missing out on,” Papalii said.
“Just seeing the likes of a few of the Penrith boys coming out and I’ve had few text messages from other players who haven’t come out yet saying they’ve put their hand up for Samoa.
