That webinar was a joke. Zero credibility.
Firstly, they state a tax return is a document required for a retirement extension using the income method.
This is false, there's never been a report anywhere to that effect. If there was -it'd be all over this forum and other places.
So simply, patently untrue.
Secondly - they state a tax return isn't required for a retirement extension using the "800k in the bank" method.
Thai taxation is based on income, for foreign income it's based on "remitted".
The 65k monthly income can come from savings ( non assessable, non taxable) or other types of non assessable income e.g. US social security, or remittance of capital.
Therefore a retirement extension based on the income method- can be qualified for with no obligation or need to file a Thai tax return.
Equally, the 800k in the bank can come from remitted foreign taxable income and therefore give rise to technically an obligation to file a tax return.
So their statements on this are simply, complete rubbish.
There is currently, no link at all between thai taxation and the retirement visa.
As much as the predatory tax agencies would like you to think there is, there isn't.