Shipping #1 - Retailer (amazon/B&H/adorama) to concierge service (hopshopgo, comgateway, vpost) is sometimes free to maybe about $10 depending how fast you want to sent. There's no tax if you sent to concierge services.
Shipping #2 - Concierge service back to Singapore. This weblink is useful. You can select Singapore, will calculate 7% gst for you so you will pay this upfront as well. But not include insurance (0.65% of declared value+shipping), fuel surcharge (about 15% shipping cost)...You can certainly use others as well.
Ohh.. Alright noted, thanks so much for the guidance here, really appreciate it. Have a great day!