I have a few relatives of a friend who work offshore and sometimes bring a kind of "used oil" or something and make extra 30-70k just like that, do we know which positions are entitled to this huge bonus ? I guess not everybody working offshore gets it.

This wasn't a straight bonus, more like selling unrefined oil on the black market or something, seems like the oil is gifted by Petronas if i understand well ?

Yeah, perhaps some got added in translation when the hubby explained his yearly bonus to his family. Didn't seem so far fetched when youngsters buy G-wagons just taking contracts and selling them cheaper to other contractors.
If it's just a standard bonus it's probably not really worth it i guess, just a disguised salary ? Like you feel like 7k is a great salary for KL, then they offer you this huge 70k bonus, you feel even better, but in reality some foreign company would be ready to pay 300-500k yearly easy for somebody with your experience.