score:5
TL;DR: Possible? Sometimes. Recommended? No.
Due to complex hysterical raisins, Singapore applies different Customs rules for visitors to/from Malaysia. So legally, the answer is clear:
You may qualify for tourist refund if the following conditions are satisfied: ...
Depart with the goods via Changi International Airport Departure Hall / Seletar Airport Passenger Terminal / Marina Bay Cruise Centre Singapore/ International Passenger Terminal at Harbourfront Centre within 2 months from the date of purchase;
Land border crossings do not apply.
Now, is it physically possible to apply for a GST refund with the automated kiosk in Changi, get it refunded to your credit card, and depart by land anyway? Yes. However: