Well that sure sucked! Got in at 6:40am and was whisked to immigration. Since we had done this exact trip previously and Thai took us directly to the F lounge/spa we had no problems with waiting in luxury until 1:15pm.
Unfortunately, as described here this is no longer the case so as arriving F pax we were dumped at the massive immigration lineup. When we finally got to the front we were told we were too early and had to wait in limbo for a couple of hours. Now were in the domestic business lounge. Anyways lesson learned, no longer need to book Thai going to Thailand as there's no longer this huge pro.
We'll just use them when leaving now.
P.S. The head steward on the plane and all his minions insisted we'd be good to go for the F lounge after I explained our scenario and mentioned what I'd heard in this thread. That got our hopes up which just made the dashing that much tougher to take.
Thanks for bringing up this major changeup for arriving F pax thaidai!