Medical for Visa

Hello,

I have a new job in Bahrain. The employer is asking me for a medical in my home country including chest x-ray to get resident visa on when I arrive. Do I have to have another x-ray and medical once in Bahrain?

Yes you will go through another full medical on entry into Bahrain.

Thank you. Is it possible to get visa on arrival if all tests etc are done in home country... or does it speed up the process?

I think you are confusing different things. If you come on a work visa, they will put residence visa sticker at the airport.  But that is subject to a medical in Bahrain later. If you don't do it or fail it, the visa is cancelled.