The former Newcastle and Southampton striker is currently serving an eight month prison sentence.
Ranger, 26, admitted online banking fraud in May and was sent behind bars.
But the ex-Premier League hitman is expected to be released within the next few weeks.
And Shrimpers boss Phil Brown expects the striker to return to training ahead of the new League One campaign getting underway on August 5.
He told BBC Essex: “When the season starts, we'll try to get games behind closed doors so he can get a level of match fitness."