The 25-year-old, who joined the Saints in January, did not make a single appearance for the English outfit in the second half of the season.
Molde are believed to have made a move for the centre-back, but Forren has revealed that he will not be returning to the club on loan.
"I am very fond of Molde and hope they do well. But right now it's not an option for me," he said in the Southern Daily Echo.
A number of European clubs have also been linked with a loan move for the Norwegian.