i'm with Veep. I hate to see folks come here, and want to pay so little for people and services. They have families to feed, dentists to pay, and school uniforms to buy.
I actually did have a little trouble when they wanted to stamp me for thirty days and I said I’m entitled to a year. They called the supervisor on the phone, they want back and forth but finally, after an hour of this they stamped for a year, and did ask for insurance. Then coming back from Lao I had trouble too. Once I got a multiple re-entry permit it has been smooth sailing this last year.
I did a round trip to Singapore near to end of my visa’s first year to get that additional year . Way easier than doing the regular renewals . But at first the immigration officers at the airport would not stamp it for another year so I had to insist they contact a superior. Then I just had to show them my insurance. Since then I have been in and out of Thailand and no problems with that additional year expiration.
Ask, and ask more than one person in immigration. Different people, different answers. Normally I would not suggest using a agent ( I never did ), but in your circumstance they might work with particular people in immigration and have connections you would not have....talk to them anyway. You may consider going on a tourist visa specifically for the purpose of dealing with folks in person, not the immigration folks really, but agents. Don't quit after one negative experience. If it fails you can try some of the options mentioned here. On these forums you will get so many different answers your head will spin - so if serious , make a 30 day trip (or longer ) . The medical thing could well be an issue - you could be asked fo real insurance guarantees ...