I was talking about about keeping the cover from your employer once you retire.
I think this is available to most US civil servants, many large corporation and the UN. I belong to the last group. The way is works is quite simple: the underwriter assesses the whole group of employees and retirees instead of assessing individuals. The premium (millions) is paid by the organisation and fully or partly recovered from the employees and retirees.
This is not uncommon at all. Then of course the question is wether this cover works in Thailand. In my case, being from a UN organisation, obviously the cover had to be international. And very honestly, if that hadn't been the case I wouldn't have retired here. As you get older having to face massive medical expenses isn't a possibility anymore, it becomes a damn certainty.