OP - immigration can be difficult at times. frustrating, etc... i've arrived in thailand from the US on a visa exempt entry (allowed 30 days, although one was 45 days as they gave that amount when quarantine was in place). i already had a bank account with the 800,000thb on deposit. it is fairly easy to go to desk C-1 and change/convert your visa exempt entry to a 90 day NON O (i've done it twice). there is rarely any wait time, desk C-1 is not busy, you are at the desk with the IO in minutes. so not a long day at immigration. i also had the challenge of being in/out of the country so often that i had to time it with one of the rare times that i was actually in thailand for more than 90 days so i would be able to do the one year extension.
it might be easier to get the NON O from the LA consulate. but once you are aware of the process to do it here in thailand, it is fairly simple - assuming you've already got the bank account and the money on deposit. you get a bank letter, your lease, make some copies of passport pages and you are all set. as noted by another, you've got to do it with at least 15 days left on your permission to stay via a visa exempt entry or tourist visa entry.