If arriving on a 60 days visa exempt and then extend the stay another 30 days at immigration, you'll have 90 days.One border run to a neighbouring country will give another 60 days. That's a total of 150 days.This is an option without any visa-application back home and just one visit to immigration in Thailand. It's doable.
You need an official address when applying for a bank account.A hotel address doesn't work anymore. Some banks wants proof of having at least a 1 year contract.It differs between banks and branches. Go for Bangkok Bank, Kasikorn Bank or SCB.
That confirmation isn't probably what Bangkok Bank means by this strange new rule. The reason might be borrowed money from agents,and they want to make it harder for them. I don't know,and I really don't care. It doesn't affect me the least. I've had my money in my accounts many years.
It's totally ok the way he's thinking.If he return back home after he opened a bank account in Thailand and over time transfer a total of 800k into his account, then when he's back in Thailand when he's retired,he basically just has to kill time until the 1 year extension. He already has the money needed in the bank,and it's smarter to apply for the Non-O back home instead of doing it in Thailand. It's only one visit to immigration.
When you get married in Thailand with a Thai lady, you register the marriage at the district office in the province where she's staying. This is very simple and cheap. When it's time to apply for a 90 days Non-O visa based on marriage and later the 1 year extension based on marriage,it's just copies of the marriage license/certificate (one per application stamped and signed at the district office) needed. In total 2 copies. A total cost of maybe 100 baht. That's all you need at immigration regarding the marriage, one piece of paper per application.Does this seem complicated to you? Like I said, it's a walk in the park.