In some parts of the world that would be an augmented crew.
In others the complement of an augmented crew would be 2 Capts, 1 F/O and 2 F/Es.
The rules I operate under would allow 16 hours duty.
A heavy crew would consist of 2 of each cockpit crew member. This would allow for 18 hrs duty subject to 3 bunks being available.
Another 3 hrs could be added to the FDP due to unforseen circumstances after sign on!
Don't know about the rules/FOM that Phuket Air operate under.