You Do Need power plug adapter while traveling from Tonga to Sint Eustatius.

Here is Why You Need An Adapter

The outlet and plug type used in Sint Eustatius are A, B, C and F and in Tonga is I. This is how they look like.

Tonga

In Tonga, outlets of type I are in use.

Type I

Sint Eustatius

In Sint Eustatius, outlets of type A, B, C and F are in use.

Type A

Type B

Type C

Type F