Yes you need to read the DTA applicable to your country. I have dual tax residency and the DTA provides a "test" to determine which country prevails. I have closer economic and personal ties with Australia plus a permanent place of residence in Australia, so Australia is the only country where my pension is taxable
There's a lot more to residency than how much time is spent in the country. In Australia for example it's more to do with having a permanent abode and family/financial ties than it is a simple number of days. If it was simply number of days, the mega rich would just spend four months in three different countries and avoid tax everywhere, so much more to it
A pension is a pension. I haven't seen any DTA which differentiates except for government employees who were working in both jurisdictions, such as embassy staff etc
It's been postponed until "next year" as the government is looking at combining the 300 baht "tourism tax" into the application process and it seems agreement has to be reached with the participating banks