like I described, I get the bank letter at the bank. But I read somewhere you can request the statement online. The app can email you an annual statement, but you would have to print it out, and whether immigration would accept it is something only your immigration office can answer.
The yearly statement takes 7 days to prepare. I had to go into the bank, request it and pay the 200 baht, then go back in 7 days later to pick it up. I then also ask for the bank letter, pay the other 100 baht, then run straight to the immigration office.
You might be able to start the request on line, which could save you a trip. May want to call Bangkok bank and see if that can save you the first trip.
I just do it for my wife. I created an account using her name and info, and file the TM30 as necessary. This saves her having to deal with the website and stuff.