there is a rule, if you wish to spend extended periods in Thailand, or come and go as you please get the correct visa - which certainly is NOT the tourist exemption - note the word TOURIST which based on your travel profile the immig officer, decided that you were not in this category which is perfectly within his rights
understand, many of us feel the same, one of the attractions for us retiring here was the tax situation , vis a vis our other options, unfortunately that door is closing, at least nothing to pay in most cases as US , UK, AU tax rates are higher………good luck
it’s very clear, a tax resident (over 180 days in Thailand) is required to submit a tax return before Mar 31st next year detailing income for the tax year. if there is a DTA in place with your home country, and you have paid tax there it will be an offset against any potential tax due in Thailand, so in most cases nothing to pay. Folks can ignore it, as I am sure many will, however the obligation never goes away, and back taxes, and penalties can be painful, not to mention all the hassle of filling out backdated returns. None of this is any different to obligations in our home countries, and nobody should underestimate the RD and the systems and reach they have , through banking systems , and relations with other tax authorities.
Joint account requires a marriage certificate and it’s also a pain to use, as for anything involving a visit to the bank requires both of you to be there. We went that route but switched after 2 h