You Do Need power plug adapter while traveling from Côte d'Ivoire (Ivory Coast) to Tonga.

Here is Why You Need An Adapter

The outlet and plug type used in Tonga is I and in Côte d'Ivoire (Ivory Coast) are C and E. This is how they look like.

Côte d'Ivoire (Ivory Coast)

In Côte d'Ivoire (Ivory Coast), outlets of type C and E are in use.

Type C

Type E

Tonga

In Tonga, outlets of type I are in use.

Type I