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

Here is Why You Need An Adapter

The outlet and plug type used in South Korea is F and in Laos are A, B, C, E and F. This is how they look like.

Laos

In Laos, outlets of type A, B, C, E and F are in use.

Type A

Type B

Type C

Type E

Type F

South Korea

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

Type F