Once you receive your visa there are no ongoing requirements provided you don’t interact in country with Immigration. Exit and re-enter for the five years validity without restrictions.
incorrect. The minimum filing requirements differ depending on source of income and status. As an example a single person filing a PND91 based on section 40 (1) income would have a minimum tax filing threshold of 120k baht. However the same single person filing a PND90 based on section 40 (2-8) income would have a minimum tax filing threshold of only 60k. So yes, absolutely, the source of funds has a bearing on the legal obligation to file.