1st Way: If you own the flat with your spouse, sell away the flat, get your cash and CPF refund, then buy a private condo each. Husband 1 Wife 1.
First, you must make sure that your flat is a positive sale.
Meaning that you already enjoy some PROFIT after you deducting your outstanding mortgage loan and CPF refund plus interest.
This is applicable ideally for the BTO owners who has fulfilled the 5 years MOP.
However, there is a risk in doing so. You must make sure that you have enough cash, CPF refund and be eligible for your next bank loan before selling your flat.
This needs proper calculation & planning from your trusted agent & banker. Most importantly, you must make sure you can afford the monthly instalment for your next purchase.