Folk should always check with their immigration office.
As stated earlier for the Non O obtained in Thailand, the funds only need to be in bank on day of application
Sadly there is always an office or 2 playing games.
Jomtien was requiring 2 months seasoning of funds for the Non O application from visa exempt entry.
Which is nonsense.
You might find this thread helpful.
It has some useful links posted by @Red Phoenix
Also note CM requires 21 days remaining on permission of stay to apply for the Non O.
If time becomes an issue you can obtain 30 day extension to visa exempt 30 day stamp
https://aseannow.com/topic/1297092-non-o-visa-retirement-purpose/