That's my position. Fifteen years here, the rule change (delaying remittance until a later year) doesn't affect me, as I've always transferred pension money the same time I received it. Never had to get tax ID or file a return. As many countrys' DTAs state pensions only taxable in "country of residence" - I retain Australian Tax Residency - it wouldn't be taxable anyway. So my head is very firmly in the sand and will remain there until the Thai tax office issues clear instructions circulated amongst expat communities. There's a lot of doddery old farts out there never use the internet and have no idea of these changes. I can also see a clear "amnesty" for a year or so, until everything is settled and communicated.
All income won't be taxed. It's dependent on each individual circumstance. A person might be a tax resident in another country which would take precedence or might only transfer pension money which may be non-taxable in Thailand. Too many variables
It's a five minute stroll to my closest PO, postage and return with EMS about 70 baht, two or three photocopies a few baht. Box ticked. I laugh when I read about people spending half a day at immigration just for a check-in..