Visa offices around the country typically interpret “rules” their way. The “official” rule is that you need 500k in a “bank account” for at least a month prior to applying for the extension. If Hua Hin is interpreting that as “in a Thai bank account” then so be it. There’s pretty much not a lot you could do about it.
Do what 90 or so % are doing and bounce rather than extending.
No visa grants you entry in to Thailand. That is up to the immigration officer that gives you permission to enter. What it grants you is the right to stay for x number of days if allowed in to the country.
Where a visa may help is that the IO recognises the fact that you have a valid visa to enter and would probably be more likely to grant you permission to enter based on that.
No visa (or exempt) entry is a given. It’s up to them. If they feel you are doing something to abuse the system then they can deny you entry. Very very rarely would happen for an actual visa but it has and could.
There are numerous visa types that people classify as a “retirement” visa.
The Non OA (or Ox) or LTR visas are indeed multiple entry visas and you can come and go as you like until their validity expires.
A Non O visa is not multiple entry (Yes I’m aware that some could still potentially be on a multiple entry one from some specific embassies prior to the switch to the evisa system).
Because you specifically mention an agent i suspect that you’re actually referring to an extension of stay based of an initial visa. Extensions are not multiple entry. You buy a re-entry permit to allow your existing stamp to remain “alive”.
If your agent doesn’t know this then you really need to find a new agent.
You get them at your local immigration office or you can get them at the airport on your way out of Thailand. The airport will charge a small administrative fee if you don’t have the copies, form and photo.
Cost is 1,000 baht for a single entry or 3,800 for multiple entries. At the airport they may only sell single entry.