I'm my similar circumstances (non-o retirement) at CW, they didn't want to see the partner that I live with. They wanted a signed copy of her ID, plus a short hand written affidavit, confirming such. I also took her lease plus a copy. My name isn't on her lease. They phoned her and confirmed verbally.
Bangkok Bank head office in Bangkok allowed me to open an account on a tourist visa 2021.
They wanted an Embassy Certified copy of my passport, you have to make an online appointment for the UK Embassy.
They also wanted proof of address, lease etc. However, I live with my partner... They accepted a copy of her housebook, and a signed copy of her ID with a short affidavit that I lived with her. Plus a copy of my TM30.
Arrive either on a tourist visa or even visa exempt.
Open a bank account
Transfer money (depending if you want retirement 800kTHB or marriage visa 400K)
Submit application for relevant Non-o 90 day visa. Follow with a 12 month extension. No need to leave the country and can be extended again. Total visa costs are 3900thb, with the banked money. Insurance cover is whatever you want as not required for a in country non-o.
People in Bangkok and other areas of Thailand have been warned not to go outside due to extreme heat.
It hit 42C (100F) in the capital on Saturday, but the national weather service said the heat index - what the temperature feels like when combined with humidity - hit a record 54C (129F).