Smith, who made three appearances for the Socceroos in 2012, has been playing in Asia since leaving Roar in 2014.

The defender spent time with BG Pathum in Thailand and Kitchee in Hong Kong.

Smith said after five years in Asia the time was right to return to south-east Queensland.

"Being overseas I've constantly kept an eye on Australian football," he said.

"I knew at some point I was coming back... I want to help the team as much as I can in terms of making sure that, number one, we're competing in a crucial part of the season."

The centre back joins the Knights, who also have ex-Brisbane Roar teammates Mitch Nichols and Shannon Brady on their books.

Smith spent four years with Roar where he won three Championships and two Premierships.

The English-born 36-year-old has also had spells with Gold Coast City, Brisbane Strikers and North Queensland Fury in the past.