The World Rugby Council will meet on November 24 to vote on a proposal to allow players to represent a second nation.
World Rugby officials want Pacific island nations to be strengthened by being able to pick homegrown players who have made their Test debuts for other countries.
Folau has not played rugby union since he was sacked by Rugby Australia in 2019 following a controversial social media post.
The 32-year-old played for French rugby league outfit the Catalans last year but is on the cusp of a union comeback in Japanese rugby.
Tonga coach Toutai Kefu, who was born in Tonga but played for the Wallabies, has spoken to Folau and confirmed the fullback is keen to play for him should the rules change.
“We’d definitely be interested,” Kefu told the Sydney Morning Herald.
“We’re not in a position to bypass players of Israel’s calibre. We’d welcome him with open arms.
“I’ve had conversations with him already in the last six months. I actually caught up with him just before he left to go to Japan.
“I explained to him where we were at in terms of what’s happening with this revisiting of this new eligibility rule. He totally understands it. I said, ‘If they overturned this straight away, you could be available for us next year’.
“He said, ‘Yeah, I’m keen to go’.”
Story first published on Fox Sports Australia