it's my understanding that Thai taxes are based on money remitted to Thailand only, and not worldwide income, but they are considering adding the worldwide income aspect.
Anonymous participant to the local immigration office where you're staying. When I got a new passport, I actually paid an agent to do this. I don't usually pay an agent. They took both my passports down and had the immigration office take care of it.
he simply asked an immigration officer what would be required for extending in country. The officer replied that you'd have to again show financials and other documents and suggested briefly going out of the country was a better alternative.
I think the part about the affidavit isn't accurate. I'm from a country that doesn't provide it, and I do the monthly transfer method. Why would they need an affidavit if the actual money is coming in?
As others have pointed out, immigration, and not the MFA will decide what's required to extend in country. Other visas I know about require you meet most of the same parameters as when you applied, and cost 1,900 or so. I expect this one to be the same, but who knows?
If it is the same, in county extensions will be 1,900 and will require you to show 500k in the bank, and if soft power, that you're still attending class.
They don't have the wherewithal to do that kind of thing at the airport or land borders. So leaving the country every 180 days might be the better option.