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

Here is Why You Need An Adapter

The outlet and plug type used in Thailand are A, B, C and O and in Swaziland is M. This is how they look like.

Swaziland

In Swaziland, outlets of type M are in use.

Type M

Thailand

In Thailand, outlets of type A, B, C and O are in use.

Type A

Type B

Type C

Type O