If his Non-B has expired then it's finished, he'll need to apply for a new one. The bigger issue is if he's on overstay. If he is, he needs to go to immigration on Monday (no later), pay the overstay fine (500 baht per day) and apply for a "covid unable to travel extension."
That doesn't make sense. He's either on a Non-B, on a visa exempt entry, or in the country illegally on overstay. And if he went to immigration, he can't be on overstay.