From star web page
Star Alliance Gold card holders and one guest, have access to any lounge that is identified with a Star Alliance Gold lounge sign when departing on a Star Alliance flight. Note: United Airlines' Premier Executive and Premier Executive 1K customers and US Airways' Chairman Preferred and Gold Preferred customers have access to U.S. domestic United Red Carpet Club and US Airways Club locations only when they present a ticket or boarding pass for a same-day international flight.
In SIN, I don't believe there's any non-*G lounge that you can access as a RCC member. BTW, what airline is SG?