You Do Need power plug adapter while traveling from South Africa to Hong Kong.

Here is Why You Need An Adapter

The outlet and plug type used in Hong Kong is G and in South Africa are C, M and N. This is how they look like.

South Africa

In South Africa, outlets of type C, M and N are in use.

Type C

Type M

Type N

Hong Kong

In Hong Kong, outlets of type G are in use.

Type G