bath condo in Bangkok. My electric bill is 2k baht on average per month, and my water bill is 200 baht. I run my AC for approximately 22 hours per day.
It doesn't matter what hypothetical laws that may or may not be passed in Thailand. What matters is the individual tax status and Thailand's DTA agreements with 61 countries.
I use 2 separate bank accounts. My Bangkok Bank is used for all visa related expenses, monthly Wise transfer, and my rent payment. I also use a Kasikorn Bank account for daily spending, especially QR payments. I can transfer money between bank accounts within seconds using their banking apps.
Unless Thailand starts forcing retirees to submit tax forms every year as a prerequisite to getting a Non-O extension for retirement, there is no mechanism in place for Thailand to tax retirees. Also if you only use credit card transactions and ATM withdrawals in Thailand, that is not considered repatriating money into Thailand subject to Thai taxes.
Hopefully, you have all your ducks in a row. The biggest hurdle will be leaving the PH. As a first time female traveler, she will be under heightened screening by PH immigration. If any of her story does not add up she will be offloaded.