no problem, visa exempt on artival, before 30 days, visit immigration office for 30 day extension, need forms, photo etc etc. This has never changed during covid.
The non O in uk doesnt need the police check and is pretty straightforward to get. Cant remember the updated regs now regarding insurance but the extensions in thailand dont require it. The London embassy website is quite good and has all the info if you dig around a little. Getting the extension in thailand is no hassle provided you deposit the 800k in good time.
As James says your alternative is tourist visa and then the non o in thailand. I did mine in the uk.