You need a copy of your passport photo page, a copy of your entry stamp, a copy of your visa and a photo. You fill out the form - not sure if it has a number. You’ll need a filed TM30 and pay 200 baht. They’ll mail it to your address on the TM30 within 7 days.
Sorry not sure which counter at CW. Will ask and reply when I find out.
You may not want hearsay, but unless you specify the actual office you use then others direct experience will probably be useless as each office has their own requirements that can differ quite a bit.