If you have already applied and been rejected for permanent residency, we would recommend to make a detailed analysis of your case, objectively see how and in what issues you can strengthen the application, fix these points and only after that reapply (on your own or with our help).
Given that Singapore is much more willing to grant PR to applicants under 40 years of age, we would not recommend delaying the issue for too long, as time is of the essence here.