You can apply for the initial 90 days Non O visa through the embassy that serves your area with monthly income if you meet the requirements.
For the first year extension of stay in Thailand there’s no legal way around proving the first year yourself by banking 800K in a Thai bank account, unless your embassy offers to provide you a affidavit letter regarding income.
(Check with your embassy in Bangkok if they provide this service. The UK, US, CAN, AUS and Danish embassies don’t, but several from Western Europe still provide this service).
Then you’re already on your second year and only will be stamped back in on your current stamp or current permission to stay in Thailand. The Non O-A visa itself is expired or used.
You’ll get stamped in for another year or as long as your health insurance is valid. After 89 days you’ll have to do another 90 days report. Regarding TM.30 you’ll need to check with your immigration as some require an update when you re-enter from abroad.
Yes, but my point is that I’m aware of people sometimes facing difficulties also with a METV but it’s normally more to that story than just a regular single METV.
Everything depends on your previous travelling history. This is the way a six months multiple entries tourist visa for pure tourism is suppose to work. If you have a history of short stay entries or travel back to back on METV’s you could easily be taken aside and questioned. A IO could also suggest or insist that you stay more time outside Thailand before you do a new re-entry. Personally I would maybe have considered to use a landborder transport company for the last border bounce to be safe.
It’s not just about the correct documentation. Krungthai demanded as an example that I did the first year extension of stay on my 90 days Non O for opening a bank account. That’s not easy without a bank account unless you get a affidavit letter from your embassy. An agent can still open for you while your on the initial visa.