You Do Need power plug adapter while traveling from Brunei to Tajikistan.

Here is Why You Need An Adapter

The outlet and plug type used in Tajikistan are C and F and in Brunei is G. This is how they look like.

Brunei

In Brunei, outlets of type G are in use.

Type G

Tajikistan

In Tajikistan, outlets of type C and F are in use.

Type C

Type F