You do not need a Thai bank account if you apply for a non O visa, based on visiting your Thai wife, outside of Thailand. When you have a non O visa you can open a Thai bank account. The 400k baht must be in your Thai bank for 2 months before you can apply for a 12 month extension based on marriage. As your non O visa lasts for 90 days there is time for this but don't hang about. Ifyou apply for a non O visa while in Thailand then you do need a bank account. This is where your confusion is. HSBC account cannot be used as it is a foreign account. HSBC only operate commercially in Thailand. There is no retail banking.
what he is saying is you can not open an account until the Non O has been extended (long stay visa) You can not open one with just a 90 day non O. My bank told me the same. The rule is redidculous because you can not extend until you have a bank account.
This was why the law was amended. Before the change you could bring untaxed money onshore tax-free if it was earned in a previous tax year but since the 1st Jan 2025 that is no longer the case. Many Thais are earning serious money online and the revenue dept is trying to catch up. This simple amendment to the existing rules has panicked the expat community into thinking it affects them but it is aimed at untaxed money and not taxed income from your home country that is covered by double taxation agreements.
With the METV visa, you still get another 60 days + 30 so you can extend the 6-month validity to nearly 9 months. So I expect it will be the same for a DTV, another 180 days and possibly + 180 which would give you nearly 6 years.