Firstly, remember that after 179 day you are tax resident in Thailand if you are doing income drawdown on your 401k, whilst it is tax sheltered in America it probably is not so in Thailand as its an equity-based investment and therefore probably taxable. I am not sure about the validity of your US health insurance, I believe Medicade etc is. Problem we all have is this is a new tax system, and no one knows exactly how it work, even the tax office. For safety I would take advice from a Thai CPA. Setting up company's using nominees has become unsafe.
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47/business-nominees-in-phuket-face-jail-terms-fines