Do you really need a base to explore neighbouring countries. Long term visas are not easy and plentiful until you reach 50. Also - be careful not to become tax resident by being present more than 182 days in fiscal year.
malaysia and indonesia also made it much harder for long term visas, the difference being indonesia (still) tolerates the border runs … Cambodia is probably easiest and only viable long term option for under 50s.
i hear they only want to see the insurance cert - what about the dosh 800K business? I think it is a great little strategy as long as you are young and healthy enough so the insurance does not bankrupt you.