I was never late for reporting every 90 days and was told I was 155 days over stay. Work that one out.... They was stapling a slip when to report again in my passport. Crazy huh. Somes not doing their job.
The funds must be in only 1 account only for immigration. You cannot show multible accounts. On one of my extensions I was 6000bt short so I had the letter from my bank showing another account to show I had the funds in a Thai bank for 3 months and was refused and was given a 60 day extension to visit family and have the correct amount in 1 account. That cost 1900 bt for the ext too. You need 2 letters from the bank 1. Funds 2. Statements. And copy of bank book. All IO offices have diffent rules. When near borders they are more strict.
insurance companies are only interested in healthy people and certainly not people with pre existing. Older is very expensive but if claimed will probably say it was pre existing anyway, Accident insurance is ok.