@Tod ********
I used the Kasikorn bank branch at the basement just a week ago when I did my yearly extension.
So definitely business as usual.
However keep in mind that the queue to issue the letter can take quite some time (could be any number of people before you, and those counters are for lengthy bank stuff). For peace of mind come early enough before your appointment.
I needed to use this branch on the day itself, because I use a fixed deposit account. Thus I can't use ATM update - unless it's on the same date of a auto-renewal of a fixed deposit.