Three years ago, my cousin was in the same situation driving without Road tax nor insurance. His car was towed to the impound, he had to make a court appearance and also he had to pay for the release of his car. He had to pay Rm 2000, why 2000? he also had illegal blacked out tinting. He went to JPJ tried to slow talk to a high ranking officer and he begged, but unfortunately the officer said IF your car had insurance coverage we could help you get a more lenient fine, but unfortunately you had neither insurance or road tax. In court he was lucky though, the judge gave him a warning and stated that if he was ever caught again without these two he would be blacklisted and would not be able to buy insurance or renew a road tax under his name.
So to everyone, if you don't drive your car for one day or 1 month just double check your road tax just in case. This can happen to anyone, and I've met people who have said I've been lucky to drive without a road tax i never get caught. NEVER say NEVER.. You can never be certain.