Max repeatedly addresses Prince Abu bin Bubi as simply "Bubi". Royalty are always addressed directly by their appropriate style, e.g. "Your Highness", or as Sir/Ma'am, with the form "Prince X" reserved for use in the third person. To address them by their personal name alone (and to get it wrong at that) would be a serious breach of protocol and completely unacceptable for a government agent.
The Chief refers to Prince Abu bin Bubi as "Prince Bubi". This is a common Western mistake: "bin Bubi" means "son of Bubi", and the "bin" is a required part of the complete last name. Calling Abu bin Bubi just "Bubi" would be akin to calling John Robertson just "Robert".