@Marty ********
. That's correct. It's not actually an affidavit (an affidavit has to be signed and sworn under oath), it's just a confirmation from your home insurance company that the minimum criteria are met (travel insurance always specifies unlimited hospital treatment, but is vague on outpatient, so the embassy/consulate in your home country needs the certification). Any extension you do in Thailand will need Thai insurance. Stamping back in for a year during the validity of the visa seems to be at the whim of the IO. The last time I did this at Chong Mek, he wanted to see insurance, and I produced my travel insurance (which I'd just renewed a few days before) and he stamped me back in to the expiry date of the insurance (which was three days short of a year).