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

Here is Why You Need An Adapter

The outlet and plug type used in Swaziland is M and in Bonaire are A and C. This is how they look like.

Bonaire

In Bonaire, outlets of type A and C are in use.

Type A

Type C

Swaziland

In Swaziland, outlets of type M are in use.

Type M