@Steven **************
I think the assumption is that working here means banking here. Even if that isn't always true, it probably is true in many cases. OA visa, as I understand it, uses banked funds in home country. It would be relatively easy for an expat using that (the first year anyway) to not even have a Thai bank and just do ATM withdrawls for cash or to keep small amouts of money in Thailand at any given time. I'd imagine that OA extensions done inside the country still needed proof of local funding, so the logic starts to fall apart there if that is the case, but perhaps that just wasn't considered.