wireless networking – electric current from Mac Keyboard when External Monitor is connected

when I connect an external Monitor (Compac x22LEDch), my keyboard start giving an itching behaviour when I touch the metal surface

now after about 2 days, my left hand has been burning like it actually has burned to some minimal strength.

I live in an area of world where electrical wirings are without proper grounding and I have no option to discharge the electric shocks.

Can someone suggest how I can get rid of it.
I use a plastic chair and everything is placed on wooden table with plastic sheet on table.