For travel advice, please look at the US embassy website sometime next week - there is a new system starting on Friday and it will take time for them to update their website.
You can get a quote off the AXA Sawasdee site without committing to pay. 30 days for a 59 year old will cost me Bt2770. I wouldn't be surprised if they are revising prices and offerings after the change to the minimum as well (their website is currently down).
Note they also cover asymptomatic infection - which some DON'T. So make sure you check.