My Mom lives in the PH. You must get visa extensions for 3 years, then you can stop. If at any time you leave the country, you will be charged 20k pesos. That's it. No red stamp, no black list.
The ads online are from crooked "visa agents" trying to sell expensive options.
I've actually been through all this with my Mom (she has Alzheimer's).
For accurate answers, you can private message the PH Immigration office on FB. It's the best way to reach them.
Chiang Mai has months of burning season. The air is so bad during that time, that many people leave and come back after. Air is still bad all year, just unbearable during burning season.
So Hua Hin tends to be dryer than most Thailand cities. This means less mold too.