BRISBANE Roar skipper Matt Smith's swansong against Adelaide United tomorrow night will be far from ideal.

The club's worst-kept secret was let out of the bag yesterday, with the 32-year-old defender (pictured) to join Thai first-division club Bangkok Glass.

The central defender, who has made 112 A-League appearances in the orange shirt, asked to be released earlier this week, despite having another 18 months to run on his contract.

The Roar received a formal offer from Bangkok Glass and yesterday agreed to terms to release Smith for an undisclosed transfer fee.

The release is effective from Sunday, allowing the two-time champion to play one last time for Brisbane, albeit in Adelaide.

Roar football director Ken Stead said: "It is a significant loss, but ... the January transfer window is a timely opportunity for the club to strengthen our squad."