"Richard has been looking to get into sports fitness since he stopped playing and has gained qualifications," Swansea team manager Ian Hopkins told the South Wales Evening Post.
Rees gained his solitary Wales cap against Zimbabwe in 1998.
And the St Helen's outfit have made seven new signings during the summer as they look to build on their fourth-place finish in last season's Principality Premiership. Up front, Swansea have signed lock Huw Alford from Tonmawr, No.8 Steffan Jones from Maesteg, hooker David Littlehales and flanker Ed Price.
Highly-rated centre Jono Stuart, who featured for La Rochelle in France last term but who had previously played for both Leicester and Borders, joins the club's back division along with fullback Warren Davies, who travellled the considerably shorter trip from Mumbles, while fly half James Dixon makes the switch from Newport.
There is also a return for highly-rated prop Tim Evans, who has made 84 appearances since his debut in 2002, but has been battling a series of injuries for the past two seasons.
"We are really happy with the signings," added Hopkins. "Steffan is only a young lad but he is a strong ball-carrier and a good athlete. The same goes for Huw Alford."