Using a valid visa there should be no time limit that you need to stay out of Thailand for.
There may be some land borders that insist when using visa exempt but shouldn’t be an issue with a valid visa and almost certainly at no airport entry.
The reason itself doesn’t matter, but if it’s for “long term stay in Thailand” Wise try to route it as an international transfer (if using Bangkok Bank) rather than a domestic transfer.
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.