What are the tax implications for Australian income if residing in Thailand on a DTV visa?

Once you spend 180 days or more inside Thailand in any calendar year you automatically become a Thai tax resident. Once you are a Thai tax resident any assessable income brought into Thailand becomes liable to thai tax and must be declared on a Thai tax return by the end of March in the following year. So whether you will be liable to pay tax and how much entirely depends on how much assessable income you bring in during the period and what credit you can claim against Thai tax for any tax already paid on that money in Australia. I doubt very much that using an Australian trust structure would make any difference to this.