HOURS LATER SAME DAY UPDATE: got my under consideration stamp until dec 15th and was told I can return for the 60 day stamp as early as dec 9th (earliest possible), up to a few days after 15th. Note: immigration closed for holiday dec 10 & 11
UPDATE ON 60-DAY EXTENSION - I've just been to immigration in Samui (living on Koh Phangan). They are only giving a consideration stamp right now, so you must return no earlier than Dec 15th to get a 60-day stamp that starts from Dec 1st. You can only get the 60-day stamp from the same office that issued the consideration stamp. There's no way around it. I asked to receive both stamps today for an extra cost and they won't do it. Must show proof of registration with current accommodation (I printed out a screenshot received from my guesthouse), several forms (TM7, STM.2, Affidavit form, one photo, copies of all relevant passport pages, 1900B.