@Billy ********
What you will have to pay for a good international health insurance during the first two years of a Non-Imm-O/A visa, is only a part of the game
Because when you go from the visa to the 1-year Extension of Stay Permit, Immigration only accepts a Thai private health insurance, listed on the tgia-list of insurances.
These 12-15 insurance companies can be easily accessed on the internet and their quotes and yearly rate are listed. You find them when you google for "tgia list of insurances"