Which bank?
I have a box with Krungsri, Pleochit, and they have a habit of doubling the rental every 5 years. It's gradually increased from Bht535 per year, to 1070, then 2140 if they follow the pattern I expect it to jump to Bht4280 next year.
Well it's fairly normal, once a fashion becomes ubiquitous then to not follow that fashion becomes the new fashion. I was quite staggered on a trip to the UK this summer to see every man and his dog was now 'inked'.
But you're not inspecting their bill are you, staff no doubt simply note they brought their own and add any corkage to the bill. These things depend on the bar, the more expensive the higher the corkage, I'd be surprised if places don't charge because obviously bringing your own booze deprives them of income.
It's quite common for people to bring their own wines & spirits to music bars in Hat Yai, corkage fee is usually Bht200. Just ask at the venue if it's OK and what the corkage fee would be.
https://www.meteoblue.com/en/weather/week/krabi_thailand_1152633
https://www.meteoblue.com/en/weather/week/ko-samet_thailand_1606720
It's wet season down south.