What is the name of the bank letter required for a Non-O retirement visa extension in Thailand?

Yes the 800 K is in a term deposit (So fixed interest account). the second 400K deposited on Jan 10th so I'm thinking going March 11. Do my TM30, Jump into extension queue, well sorta lumber slowly into it actually, get my extension queue number then go bank and get passbook updated and both letters then back upstairs to wait. If it gets too late can always go back the next day. And also if the CW branch tells me to go to account holding branch, will do that and go again another day. Do you know how long the TM30 overdue queue takes?

I will get the guarantee letter first, so can do that at the CW branch? when I go and sort out my TM30.

So the branch at CW will actually do both letters Tod? That's good if correct. Saves yet another trip to a bank to take a queue, pew, phew while mountains of dead trees are ruffled and stapled.