OK TK, your point makes sence.
I checked in late once and couldn't get it. No big deal, as I was in C.

3 times, I've got it though. I've had to specifically ask for it, and although surprised at my request, the boarding pass popped out everytime without any second set of questions.

I think that most pax think about it. They don't offer F seats to everyone, I'm assuming. The times the cabin isn't full could perhaps mean not enough people asked.

Coming in the last time, from HKG. I checked in in HKG for HKG-BKK-HKT and asked for 1K on the HKT portion. She said 1K was blocked (dissapointment), but 2A was available (happy again). Funny on the flight, that 1K and a few other seats were empty. Got me thinking... maybe they block for VIPs. Who knows. But there's more than meets the eye, as is usually the case in Thailand.