Compatibility summary
You will need a travel adapter in Guyana; plug types used there differ from Singapore.
Plug comparison
Singapore plug types: G
Guyana plug types: A B
There is no common plug type between Singapore (G) and Guyana (A B). You need a travel adapter.
Voltage comparison
Singapore: 230V, 50Hz
Guyana: 220V, 50Hz
Voltage difference is within a range many devices tolerate; check your appliance label.