The defender has been in impressive form for Gus Poyet's men, helping Albion climb up the table after a poor start to the season which had seen them drop into the relegation zone.
The 23 year old signed for Swansea under Kenny Jackett initially on loan from Birmingham City and the left back became a solid part of the League One title winning team of 2007/08.
A cruciate ligament injury early on in the following season kept him out of action for almost a year, before he returned to action in the Carling Cup against Scunthorpe last August.
His last Swans appearance came in the 2-1 FA Cup loss at Leicester in January.
"I'll always remember the good times at Swansea,'' explained Painter, "especially the promotion campaign from League One.
"Apart from my injury last season it's been really enjoyable. The fans have always been brilliant with me and I will miss them.
"But I need to play regularly to push myself back into the Championship again, hopefully with Brighton.''
Planet Swans would like to wish Marcos the very best for the future.
This article first appeared on JACKARMY.net.