they use to have these coin counting machines at banks, they got rid of them. So clearly it wasn't worthwhile for the banks. There might still be one left at SCBX Park.
How long do you want to stay in Thailand? If you're a tourist then the best or easiest option to stay a while is probably the METV which is a multiple entry tourist visa where you get stamped in for 60 days each time you enter, this is valid for 6months. You can stay almost 9 months with this visa if timed perfectly, add a few land border runs at the end and you could stay a year.
Otherwise there's the expensive options others have posted.
that's good, so all he'll have to do is talk to military department at District office, they'll make him pay a small fine (couple hundred baht), then discharge him to the inactive reserve unit as he's over 30.
Idk about entering on an expired passport, but IF he can get his ID card then he can just overstay on his foreign passport and they will waive the fine.
I'll let others speak as to the non o and documentation requirements, though possibly the 60 day family extension may be available. Though it might require Thai ID, I'm not sure.
You should join Thai Citizenship Group, if you're after info on him obtaining his first Thai ID card.