I doubt he can apply for a 60 day covid extension either to allow time to find a new job. The only way of extending his current visa is with a work permit with his current employer. It looks like finding a new job and getting a new non b in the next month is his only remain in Thailand option.
I think it's been realised that the Embassy letters were a farce, and what's needed instead is first-hand evidence that the applicant genuinely can't leave Thailand so needs a special extension to avoid overstay. Very few will have this evidence, because most can leave but don't want to.
Good luck. It's not a worthless comment if other members heed the advice. Those that went down the agency route will currently be facing the most probs, as their only aim is to get your cash.
And the moral of the story is - don't wait until 4 days before your visa expires to start planning. Why do you think you'd be allowed to stay just because the border is closed?