When searching, check the 'Ship to Singapore' box, and on the product page look for

Price: $199.99 + No Import Fees Deposit & FREE Shipping to Singapore

For example, this GTX1060 graphics card is eligible - https://smile.amazon.com/EVGA-GeForce-Support-Graphics-03G-P4-6160-KR/dp/B01KUADE3O/

You get free shipping if your order is over US$125, and the price can be a lot better than Sim Lim Sq. The downside is that shipping can be a bit slow, up to 2-3 weeks, but if you're not in a hurry it's well worth it.