Compatibility summary
Your Thailand plug may fit in South Africa outlets, as both use at least one common plug type.
Plug comparison
Thailand plug types: A B C O
South Africa plug types: C D M N
Both countries share at least one plug type (A B C O and C D M N), so some plugs may work without an adapter. Check your appliance.
Voltage comparison
Thailand: 220V, 50Hz
South Africa: 230V, 50Hz
Voltage difference is within a range many devices tolerate; check your appliance label.