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

Here is Why You Need An Adapter

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

Singapore

In Singapore, outlets of type G are in use.

Type G

Liechtenstein

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

Type C

Type J