You Do Need power plug adapter while traveling from Gambia to Lesotho.

Here is Why You Need An Adapter

The outlet and plug type used in Lesotho is M and in Gambia is G. This is how they look like.

Gambia

In Gambia, outlets of type G are in use.

Type G

Lesotho

In Lesotho, outlets of type M are in use.

Type M