Don't know what country you're from, but Australian DTA the pension is only taxable in the country where it's paid, so tax credits don't come into it which is just as well as Aussie pensions are tax free after 60. I'm also an Australian Tax Resident, so the DTA gives precedence to that over Thai Tax Residency
Pensions are generally attached to employment. I don't know of any pension scheme which is not associated with employment, except state pensions which are associated with residency, citizenship etc. The Australian DTA has no reference to employment, so the Australian age pension would also be exempt from taxation in Thailand
It says "pensions" which is all pensions, except government pensions which are subject to article 21. Sorry to say, you're not the sharpest knife in the kitchen drawer
Many pensioners ARE ok! There's a few (mainly British) who aren't. As has been pointed out US, Australia, NZ, Canada, Germany are all good! That's a lot of pensioners! 👍👍
Report by mail is 100%. You have the EMS number so you can track when it arrives at immigration. I've used for many years, never had a problem. I can't be bothered to hike out to Chaeng Wattana for such a simple task. The TM30 is only a notification online. You can print it as soon as its done. I do that every time