Do you have a link that says you do with the DTV Visa? The visa gives you 180 consecutive days before you either get another 180 day extension, or leave and re- enter and get another 180 day stamp. This is a visa, not an O visa extension, which requires ninety day reporting.
Best thing to do depending on whether you have any pre conditions is to have a full medical, blood tests for liver, kidney, cholesterol & blood count. Also lung x ray, echocardiogram, Myocardial perfusion scan, which measures the blood flow through all arteries & blood vessels of the heart to see if there are any problems. Also there are blood tests these days to see if you maybe susceptible to some cancers. If you have these and get the all clear. Then just hope your plane doesn't crash on the way, or you don't get in a road accident once in the land of 😊 😂 😂 😂. Seriously though even if your in your later years, like myself & are in very good physical condition, weight & BMI, then even if you want some peace of mind with some sort of health insurance, try to get the impatient only cover, with the lowest patient cover, IE., 400,000 baht. Also to keep your premiums down accept whichever excess you are comfortable with. I lived in Thailand from the age of 50 to 61, never had health insurance, saved a fortune, but took the risk. Now I'm 76 & hoping to go back early next year & will not be taking out insurance, mainly because it doesn't matter how fit & healthy I am, just the fact of my age means the insurance companies look at people like me as a bigger risk than someone in their forties that might smoke, be overweight & physically inactive. It's the same in any walk if life D.O.B matters more than the condition of a person.
Ok, so on that basis you can stay for a full five years? Just do a border bounce on day 360 each year. Which would be good, unless you came across an IO., who wouldn't let you in because you were returning on the same day as you left.
People need to do their homework before commenting. With the DTV you do NOT have to leave after 180 days. You go to an immigration department and get it extended for another 180 days, then after 360 days you have to leave for 5 days, which adds up to one calendar year, then you can enter again and go through the same process and for another four years.