If the crew pushed from JED at
1120 Z on the 4th and flew to Dakar and arrived back in JED at
0625 Z on the 5th, I come up with 19:05 hrs Duty, plus 1 hr prior and 30 min after for 20:40 duty which doesn't add up for a JED/DKR/JED turn.
This is more likely to be the Block hours, not Duty hours ? Please expand further if you can.
Sounds like an out of control scheduling department or non existant one, "still".
Illegal crewing. 
What are the crews thinking when they accept this kind of rostering, don't they know that their very own licenses could be on the line ?
When are the Saudi's going to put a stop to this. Perhaps it will take intervention by ICAO or other governing bodies as the Thai's don't seem to give a S--T.
Sounds like this Phuket Air crew got lucky , again.
Sooner or later the luck will run out with this operation.