A question about income taxes (the fun stuff...)

My little cousin f-up and left the country in a rush without paying his income taxes. He was a tax resident in Taiwan the year before (meaning he was in Taiwan for over 183 days on the year where he should have paid income taxes), and because of that his employer did not withhold taxes on his salary which he should have gone and paid before leaving. His employer did declare his salary normally to the tax office.
He is wondering what is going to happen to him if he comes back to Taiwan for holidays.
Anyone got experience with this?

he’ll be made to work 12-hour day-shifts at the 7-Eleven right next to Fulong TRA station entrance during summers until it’s paid off in full along with interest.