ThoughtfulLychee5096 Thailand is not a third world country, this classification is outdated anyway, but if you still want to use you should classify Thailand as "second world" and the average salary is about USD 375, but that is irrelevant because they don't want to attract average Thai salary people.
Just look at requirements for other visa and you can conclude THB 65k is what MFA thinks is appropriate as monthly income.
For some reason they have doubts about your job and income.
You mention you showed income from a "foreign" company.
Did you show a contract with salary mentioned in it?
Did you show monthly payslips?
Remember it is not up to you to decide the money is enough to live in Thailand, but up to them, you did not mention anything about the income, only that it is less than average, but not if it is substantial less.
Anonieme deelnemer Personally I think they are afraid that with such a low salary you want to work illegally in Thailand, and therefore finding reasons to reject you.
Tax residency in itself is very simple, stay at least 180 days, not necessary consecutive in a calendar year in Thailand, and you become tax resident, regardless of type of visa or bank account or no bank account.
What are the consequences of tax residency is a far more complicated story, depending on your personal situation, nationality, DTA and more, so if you plan to stay longer than 180 days on a DTV just find an expert for advice.
I miss that you showed a letter that you are allowed to do remote work from Thailand, but when they rejected you because of income that should not be the reason.
Alternative for downloading is filing TM47 online, and when it got rejected because it is the first one of stay, just print the online filled form and take that to the immigration office.