A smiling but silent Sonny Bill Williams has returned to Australia almost 10 months after walking out on the Bulldogs NRL club.

The 23-year-old New Zealander, who left the Bulldogs last July to accept a big-money offer from French rugby union club Toulon, was greeted by a large media pack as he emerged from customs around 7.05am on Thursday (AEST).

No stranger to media scrutiny, a beanie-wearing Williams managed a smile but didn't answer any questions.

Flanked by several minders, the former New Zealand rugby league player was hustled through the arrivals area and into a waiting Range Rover.

Williams is scheduled to turn out for rugby union's best-known invitational side, the Barbarians, against the Wallabies on June 6 at the Sydney Football Stadium.

He is making a brief stopover in Sydney before leaving later on Thursday to head to Brisbane, where he will make his professional boxing debut next Wednesday.

He is due to fight his fellow New Zealander Gary Gurr on the Brisbane Entertainment Centre undercard of the middleweight world-title fight involving his friend Anthony Mundine and IBO champion Daniel Geale.

Former WBA super-middleweight titleholder and rugby league star Mundine is believed to have paid a substantial sum to the Bulldogs to help facilitate Williams' release from the NRL club.

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