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.
In the past they have asked for proof of residence, plus the local embassy validates your vaccination certificate, so you're going to want to have been vaccinated there too.