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

Here is Why You Need An Adapter

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

Swaziland

In Swaziland, outlets of type M are in use.

Type M

South Korea

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

Type F