Old codger is cruising for a bruising.
This is no place for an old, poor, sick (or sick to be), lone farang. As far as I know, he has to cross a border to clear his overstay.
On his return, it's almost guaranteed that he will be denied entry.
Catch 22.
He can try to show up at immigration asap, explain his negligence and hope for the best.
An agent can inquire on his behalf, if he chooses so.
Doesn't look good.