It doesn't matter whether it is a different company or not, since your supervisor (the CEO) has a right to tell you to perform work for other entities. It also does not matter whether a different employee would be paid for the work or not. All that matters is your own pay "classification":1) If you are an hourly employee, you must be paid for all hours worked--i.e. for all  work your employer directs you to do, no matter who the work is for. You must also be paid overtime for hours worked over 40 in a week, as applicable.2) If you are salaried and exempt from overtime, your employer may make you work any number of hours, for any entity, without additional pay.3) If you are salaried but not exempt from overtime, then you should get additional compensation for hours worked past 40 in a week; but for hours under 40, it doesn't matter what entity you're doing the work for.As you can tell from the above, not all salaried employees are necessarily exempt from overtime; to be exempt, the employee's duties or responsibilities must also pass certain tests, which you can find at the federal Department of Labor website. If  you are an hourly employee, or believe you are salaried but not exempt from overtime, you may have a claim for additional compensation and should speak with an employment law attorney. Good luck.