Unless he already has a Thai bank account, he cannot get the non-O inside of Thailand. You are required to show the funds in a Thai bank account to apply in Thailand, and cannot open a bank account unless you already have a long-term visa.
He might be able to show a combination of things to get the non-O visa at the Thai embassy, but that won't help him once he gets to Thailand. For the first 1-year extension, the only option available is showing 800,000 baht in his Thai bank account, or embassy certified income. The US embassy does not do income certification, so the 800,000 in the Thai bank is the only option.
The other option he has is using a visa agent, but that's going to cost anywhere from 30,000-50,000 baht for the first year.
I told you, the ONLY extension you can get is the 1-year extension. There is no other extension available to you. After that you will need to leave Thailand.
You can try returning on visa exempt and see if your immigration office will allow you to apply for a new non-O visa in Thailand. Some offices allow this. It will require a few extra trips to immigration though.
First you apply for the non-O Visa, then you get an "under consideration" stamp with a date to return. You return on that date and get the non-O visa in your passport. Then you wait until 30 days before that time is up and go to apply for your 1-year extension.
no, you cannot just get a random extension from a non-O.
There are only 2 extensions available. The 1-year extension and a 60 day "visiting Thai family" extension if you have a Thai spouse or half Thai child. Since this person only mentions 800k then they are getting the retirement visa, so there's no assumption they are married to a Thai.
then your won't work. You cannot apply for the non-O visa in Thailand unless you have a Thai bank account. And you cannot open a Thai bank account as a tourist. You would need to get married first and then leave Thailand to apply for the visa from a Thai embassy.
Also this is why you give all the details in the original post, because no one can properly answer your question without knowing the details.
There's a very simple solution. Don't apply for visas from the Thai embassy in NZ. Go to Vietnam or Laos or somewhere else and apply for your Thai visas. Take a trip to Bali and apply online through Jakarta. You can even make it 2 vacations in one.
And a retirement visa is not something people generally apply for every year. They apply ONE time for the visa, then get a 1-year extension each year in Thailand.
It's your responsibility to get everything done fast enough to get the money in your bank account so it's there for 2 months already in time for you to apply for your extension.
If you do not get your 800k moved into your Thai bank account in time, you have no options. You must leave Thailand and start over with a new non-O visa.
I guess technically you have the option of using an agent, but that would be a lot of money for something you can do yourself by leaving and getting a new non-O visa.
Most immigration offices only need a TM30 to request a certificate of residence. So you should have been able to get that within days of arriving in Thailand.
Then after you leave, apply for a non-O visa from a Thai embassy through the e-visa system. Then when you arrive in Thailand you are guaranteed to not have any issues and you'll be ready to apply for your extension after 1-2 months.
The only way your plan works is if you ALREADY have a Thai bank account. And even if you do, it's going to require AT LEAST 2 extra trips to immigration which is not a pleasant thing for most people.