What makes me worry is that thai authorities constantly change the rules. How can you plan anything that way, without legal security ? I am retired since october. I came to Thailand at the beginning of january with a 3 months Visa non O and asked in Bangkok for a 1 year extension which I very easily got. That extension expires in april 2020. I went back to France, where I am now, at mid april (after a 3 months and half stay). What I intended to do with my 1 year permission to stay (and later renewals) was to come to Thailand whenever I wanted. Next planned trip in november for 3 to 5 months). For now I do not intend to live in Thailand but to stay there 6 months a year ( about 2 times 3 months). May be later I would settle there. If I stay out of France no more than 6 months, the french national security system still covers me. I just have to ask them for refund of medical expenses when I go back to France (and an extra "assistance" linked to my Visa Pemier Card provides me with an advance of funds if need be. I only have to pay for an extension of this assistance if my trip is longer than 90 days). So I do no need an extra health insurance and I much doubt the french national security system (Sécurité sociale) would give me any document, acceptable by thai authorities, to prove I am already covered.