Notarization here is not the same as you may be accustomed to in 'merica. Check in with them before going to the expensive and time consuming effort to do so and see what they will accept.
Generally there are English speaking staff in the larger branches. Best to keep your financial details as confidential as possible and not involve other people. Just a word to the wise.
I am in Chiang Mai area so can't help you there. Usually it is best to go to a major branch as the staff there will be more accustomed to dealing with expatriate customers.
Bangkok Bank is generally the most understanding (and greedy for your business). From anecdotal gossip it seems to be up to the branch manager's discretion so you may need to try a couple of branches. Bangkok Bank is also handy for 'mericans as you can arrange transfers from the US through their NY branch.
David Broadfoot Have my yellow book now so no worries on the certificate for me. CM used to give them (residence certificates) to you after a wait of maybe 15 minutes...