Much easier to open non-O in your own country using home country bank account balances to prove the required economic solvency by the local embassy. Arriving to Thailand with Non-O visa should not be a problem to open a bank account during month 1 to season funds during months 2 and 3 before applying for first 1 year extension. Not sure why would anyone apply for non-O in Thailand being so much more complicated, cumbersome and prone to local IO’s interpretation of requirements.
I am not sure why not to remain on Non-O. If just to avoid the 800,000 deposit they are certainly aware of this scenario and they do not like it. You could’ve extended non-O on 65,000 per month remittances.
I would not dare to even think about overstaying in Australia or USA or Canada … even a day. Why would Thai rules be any different: plenty of time to re-enter within 180 days or simply taking a local bus from Ekkamai to Poipet at maybe 100 baht travel there. An overstay stamp is never a good thing in your passport or on your records.
the agents have a huge commercial interest AGAINST the DTV visa. They will try to get you on a more lucrative visa. I however can see the DTV visa becoming a liability the ED visa became.