They are accepting them now. And the ONLY combination of marriages that avoid the financial requirement is Thai man married to foreign woman. Every other combination still has the financial requirement.
First of all, how are you in Thailand now? Did you enter on a non-O visa you obtained from the Thai embassy? And was that based on marriage?
For marriage extension, the money must be in YOUR Thai bank account. Some immigration offices will accept a joint bank account (and some will not) but for joint accounts, you would need double the funds of 800,000 because only half of that is yours. I've never, ever heard of an immigration office accepting the wife's bank account for a marriage extension.
But none of that should matter because you're going to be using embassy certified income. That should bypass any bank account requirements.
I'd still recommend getting your own bank account, because all of the banks have locked down the accounts to only allowing one phone per account. So if you ever want to pay with QR code you would need your own bank account with your own bank app login.
nothing ever guarantees entry except for a Thai passport. There are reports of people with multiple entry tourist visa being warned. Tourist entry is tourist entry, whether it's visa exempt, single entry tourist, or multiple entry tourist. None of them are intended for long term stay in Thailand.
those have been halted for months already. No one knows when they'll resume. The border with Cambodia is closed due to the conflict. They've been doing overnight drives to Laos lately. I'd much rather go to Bangkok and get a flight than spend 18-24 hours in a van.
Yes. Though Hua Hin isn't exactly well situation for border bounces. Closest land border would probably be the boat crossing into Myanmar at Ranong/Kawthoung. Probably easier for him to fly somewhere especially if he wants to take a mini-vacation. Both Kualar Lumpur and Singapore have visa-free entry. Taiwan, Hong Kong, and even Korea and Japan aren't too far off.