I feel something strange such as static electricity when I touch the TV.

The metal parts of the TV can create a small amount of static electricity that is not harmful to human body.

To reduce this effect, unplug the power cord when cleaning the TV.

The presence of static electricity on the metal surface of AC powered product is normal and it does not pose a risk to the functionality or safety of the device.
Household electronic products such as Television are tested to specified safety standards and affixed with the SAFETY Mark before they can be sold in Singapore.

You may refer to this website for more information related to SAFETY Mark.