you are not employed or carrying out business in Thailand on a DTV. To be classed as working and have your domestic income from day 1 be subject to tax you must hold a work permit. Your whole argument is nonsense. Only your assessable remittances may be taxed on a DTV.
The DTV in many cases is stamped employment prohibited even when you apply as a workation, working remotely on a DTV you are NOT classed as working in Thailand for tax purposes therefore you are NOT earning a Thai income and will not be liable for tax provided the income remains overseas. Thailand only taxes foreign sourced income on remittance.