Compatibility summary
You will need a travel adapter in Papua New Guinea; plug types used there differ from Singapore.
Plug comparison
Singapore plug types: G
Papua New Guinea plug types: I
There is no common plug type between Singapore (G) and Papua New Guinea (I). You need a travel adapter.
Voltage comparison
Singapore: 230V, 50Hz
Papua New Guinea: 240V, 50Hz
Voltage difference is within a range many devices tolerate; check your appliance label.