You will have to provide proof of where you will be staying and for how long in each place.
Me and my wife went to UK for a month in 16 for the wedding of my daughter, we stayed with a friend in London, then a hotel in Norwich and then on to Scotland.
I got a letter and passport copy from the 2 friends I stayed with and included a copy of the hotel reservation and a copy of the wedding invitation.
Be familiar with the details on the visa application. When we arrived at Heathrow I went though the non Brit channel with my wife. The IO was very friendly and chatty, but with a purpose. He was asking in a conversational way about info we have on the application. We hadn't BS about anything, so it wasn't a problem. I presume he was looking to see how I answered his questions
I am applying in Kanchanaburi and I had to have my passport certified by the British embassy in Bangkok. You get the forms online at the embassy web page and there are links on there to make payment. You can't do it in person at the embassy Andy more.
When I was there I needed local currency for the hotel, the taxi driver knew exactly where to go and actually got us a good exchange rate. Give it a try, they know all the best places
I opened an account with SCB many years ago, so things might have changed.
I was being refused because of the wrong visa type, so I showed the clerk my pension docs and told them that amount would come in every month until I died.
They took my docs and passport and went and spoke to the manager, when they returned I had an account.
I was also accompanied by a Thai speaking friend. Good luck
When I was a Thai newbie a friend put me in touch with Siam Legal, who, for a fee accompanied me to CW immigration to get the initial 90 non imm O, (I was on a TR60 back then) and about 3 months later they call you up and take you back to immigration.
The lady who dealt with me did all the negotiating with the IO on both occasions. I sat in the waiting area and watched.
I realised that it was not difficult to do and have done myself since then.
This was a very long time ago, so I do not know if they still do this or how much it would cost. But, at the end of the day I had a 100% legal retirement visa