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

Here is Why You Need An Adapter

The outlet and plug type used in Chad are C, D, E 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

Chad

In Chad, outlets of type C, D, E and F are in use.

Type C

Type D

Type E

Type F