You Do Need power plug adapter while traveling from South Korea to Swaziland.

Here is Why You Need An Adapter

The outlet and plug type used in Swaziland is M and in South Korea is F. This is how they look like.

South Korea

In South Korea, outlets of type F are in use.

Type F

Swaziland

In Swaziland, outlets of type M are in use.

Type M