The Lounge is very busy in the night.
In the morning much fewer TG-flights leave BKK offering F-class (to TYO, HKG and sometimes SYD)...thus the lounge is not as frequented as during night.
You should switch your PHUKE-BKK-Flight to 1pm - it's much more relaxing also concerning your (pre-)travel on Phuket island and at the airport (less busy).
be aware: the F-cabins on the various B744 to/from SYD are not "harmonized" - it can be a suit like on the A380 but it can also be a traditional seat like in the old times....