There is always a financial requirement for the Non-O. But if you apply from your home country, you can use proof of income or bank savings in your home country as documentation that you fill these requirements.
The amounts required will depend on if you are applying for the Non-O based on retirement, or Non-O based on marriage to a Thai national.
There are other Non-O visas, but retirement or marriage seems to be the most likely path for you, so not mentioning the others.
However, I answered this while sleep deprived and didn't read things through properly.
I am already on a extension of stay based on marriage, and I have a account from before. Just want to open another one for saving.
But the required documents for me will be the residence certificate, my marriage certificate ( I got married in Thailand, foreign marriage documents will probably require a bit more ) and my passport.
Kasikorn in Cha Am.
I will try to remember to ask them how to proceed if one does not already have the extension of stay.
I would probably get another account in another bank to transfer the money to another Thai account before shuffling it out of Thailand and back to your country ( Norway? ).
That way the income-account stays "clean" of outgoing transfers out of the country. And you can say something like you prefer to keep it this way for the ease of documentation or whatnot. IF they even care to ask.
The Non-O is "the retirement" visa, or the "marriage" visa, depending on the route.
But, to get it inside if Thailand you need to have had 800k baht sitting in your bank account for 2 months already.
OR your Embassy writes a affidavit as a proof of your income/pension. But a lot of Embassies have stopped this service altogether.
The US for example, no longer provides this.
So you will need to get a Thai bank account.
To get a Thai bank account you will need a long term visa ( like the Non-O )
They will NOT give you a bank account on a tourist visa, and agents are struggling opening them for tourists too.
It will be much easier if you apply for the Non-O before you leave.
Enables you to theoretically open a bank account when you arrive, which gives you just enough time to season the money required.
If your embassy does not offer the affidavit, and you do not have the 800k, you could always go with the Non-OA. The Non-OA, if you time your last entry properly, can get you close to 2 years in Thailand to sort out bank and start transferring monthly a minimum of 65k baht for 12 consecutive months before your application to extend your stay further.
The Non-OA does have more requirements though. Including health and police certificates, and mandatory insurance.