Bangkok does not require the addl requirements

if you leave to your home country and not come back it does not matter. If you apply for another visa straight after ED than the Thai Embassy will check if you have cancelled the old extension of stay.

at Mae Sai, yes. Other border might be different, especially Poi Pet.

no problem, but they strict on the TWO land border in one year, other than than, no problem.

That answer only the Immigration in your juristriction, after checking your documents, can answer.

yes, but it depends on your passport, if over 6 month validity, no previous warning stamp than it should be no problem.

another reason for requesting original OP to include the Nationality as well. Thank you

I close comments as subject is clear. The statement from visa company is rubbish. They should have known.

we are a visa run company and , already, since 2014, we have been advised that South Korean can not do a border run at Thai-Cambodian border or at Kanchanaburi. We have never been shown a notification, I think it has multiple reason which I not want to list as this is guesswork only. The message is either Fly OUT/IN or get a proper visa. Sorry.

sorry, before this spirals out of control, I close comments. I see nothing wrong on the part of Thai Consulate HCMC.