Given it's a PE ticket your SQ fare-class might be eligible for a *A upgrade award. SQ will need to have upgrade award inventories for Biz class released though which is a long shot. But worth a try? It will cost you 1,550 APD for SIN-AMS.
You can try requesting one here:
https://www.airnewzealand.co.nz/nona...Redemption.jsp