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