Related question, as I'm also considering switching to Non-O. Are there any differences or advantages to applying for the Non-O in-country versus out-of-country? Are the requirements the same either way?
Yes best option is apply online for the single entry tourist visa (60 days). Or they could do a trip to VN, Laos, KL, while here to sight see and reset their 30day.
I'm based in BKK. I did several int'l transfers (totaling 800k) last year - so I presume my Thai bank has a record of that. Trouble is, I withdrew the funds to Bitkub (a local crypto exchange) so when I re-deposit them to my bank acc, I guess that could be an issue.