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

Here is Why You Need An Adapter

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

Bhutan

In Bhutan, outlets of type C, D and G are in use.

Type C

Type D

Type G

South Africa

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

Type C

Type M

Type N