“Here in the US everyone has a QR code for vacs” is untrue. States that have a digital database or QR code do have that. Some limited clinics may provide you a website (QR) where you can view your vaccination but I’ve never seen that.
I’m not sure what you were trying to say but the way you phrased that would certainly suggest that the US has a QR system (digital database).
The US does not have a federal digital database (QR code) system and never will. At least not a mandatory one. Some states have a digital system but many do not.
As to your second point and question, yes you can go Visa exempt but, you still need a Thailand Pass and that is the point at which you are required to submit proof of vaccination
So I priced out insurance at AXA for 69 days and it came to 6200 THB. So far that is the most expensive of three quotes. And its not even close actually. Given the number of people that recommend and use AXA, I am somewhat suspect that I did something incorrectly or that there is an anomaly ATM on their site perhaps?
As an example Tune was 7500 for an entire year and Safety Wing was 5057 THB for coverage that includes several other benefits in addition to the COVID coverage.