I have now received information from my immigration office over the phone that the easiest way is to make an online appointment in the Central World Shopping Mall on Sukhumvit Road.
I was unsure the last time I visited immigration because they mentioned various places where I could do this.
Last week I paid an annual fee of 599 Baht for one year including a small accident insurance for my newly opened account at Bangkok Bank. Without insurance I would have paid 399 Baht for one year annual fee. I think every branch has different conditions or requirements. I opened the account in Mukdahan. It took 1.5 hours until I had my bank card and account book in my hand.