Possible Clues:

• Country controlled by British? That's over
• Its sultan is famously very wealthy
• Be including race, I concluded, in the country
• Swinging attracts character here in SE Asia
• Manage to live without one major source of oil
• After a run, an Aer Lingus flight seeing land on Borneo?
• Eastern land controlled by British, that is, after revolution
• Sultanate in northwest Borneo
• State on Borneo
• It borders the South China Sea