They will 100% turn you away... They've even got an A4 display (in both the T2 and 3 lounges) on the counter written in big writing saying that Star gold customers don't get access prior to Silk Air flights (no exceptions even if SQ coded).
As a VA Gold, I get access prior to Silk Air flights but they wanted to check (and were quite strict about it) as on the boarding pass it just says "Partner Gold", something you most likely won't get printed on the Silk Air boarding pass.