How do you ask for job employment opening through telephone?

Rule one: don't worry about upsetting him. If you have relevant skills and experience that lead you to believe you qualify for a position (whether or not one may exist), approach the individual and make an inquiry. Be ready to sell yourself to the individual in question. Have a resume or some kind of documented work history or skills inventory ready to hand over on the spot. If you're any good, if you think you'd be of worth as a part of the organization to which you are applying, they'd be fools to pass you up. Do not burden yourself with worrying about upsetting someone by asking for an employment opportunity. If you follow a thoughtful and prepared approach which is modestly considerate and the individual becomes upset, that's his problem, not yours. You do what you need to do and let the chips fall where they may. Good manners coupled to honesty and directness go a long way. Good luck.