I think fast track entry at BKK has gone for all J passengers. Not sure about F. (I have only ever arrived in F on TG and that was years ago; we were taken by buggy to the diplomatic immigration line. Some staff collected our bags for us off the belt.)

Fast track for J was always a bit odd, took longer to get there and there could be queues. I usually ended up in the normal immigration and it has always been quick for me.

Still fast track for departure.