It's not tricky at all, it's easy. My bank asks the transit bank for the transfer details, they send them over, I go and collect and then show immigration
I am in a similar situation, one of my pensions is paid into Citibank in BKK and then transferred to my SCB account. SCB contact Citibank for me and get statements for immigration showing the payments as international. I think it takes them about 3 working days to arrange.
They have been accepted in CW, BKK and in my current office in Kanchanaburi
I don't use an agent, I do it all myself. If you have the money coming in each month why throw it away on an agent?
I used CW for many years to extend my visa up until 2 years ago and always showed a 3 month contract, mind you, the address didn't change from one year to the next.
I got the owner to do a new TM30 before each visit and he always asked me to sign a new contract, but it was never for a year.
Things might have changed since I moved out of BKK though
It's not so much the police, it's the insurance. If you have an accident and only have a licence from your home country (no IDP) , there's a good chance they won't cover the claim
I have a First Direct bank account in UK without having a UK phone number, the only phone number I have is my Thai one. The bank has no problem with this and have called me on it on numerous occasions.