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

Here is Why You Need An Adapter

The outlet and plug type used in Bangladesh are A, C, D, G and K and in Tonga is I. This is how they look like.

Tonga

In Tonga, outlets of type I are in use.

Type I

Bangladesh

In Bangladesh, outlets of type A, C, D, G and K are in use.

Type A

Type C

Type D

Type G

Type K