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

Here is Why You Need An Adapter

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

Liechtenstein

In Liechtenstein, outlets of type C and J are in use.

Type C

Type J

Brunei

In Brunei, outlets of type G are in use.

Type G