Border officer does not check the previous stay 90 day report or TM30 …. Only immigration office inland when renewing or extending the visa which is irrelevant to DTV as you have to leave at next 90 day report in any case (visa valid for 180 days only).
you must be a resident for tax purposes first for Dual Taxation agreement to come in force (telling you how taxable amounts are treated … eg civil service pensions are fully exempt in some
it is remitted funds which become taxable subject to being a resident for tax purposes and credit offset for any tax already paid in home country if there is a double taxation agreement.
They may well be below the threshold….while i would not want to be ever investigated by the tax authorities in any country …. I will stick to below 180 days presence per calendar year in the country