I don't know about the GST over there. What I am saying is that when u come back, whatever goods u bring in, over and above your entitlement of S$300, is subject to 5%GST. For instance, u buy back a new camera worth S$2,000, the customs will ask u to pay 5% GST on the S$1,700 (S$2,000 minus your entitlement of S$300).