Should I tip my driver in Manila when somebody else is paying?

I'll soon visit the Philippines for business, and our local partner will be providing a car and driver. I have no idea how much he's getting paid.

Should I tip him, and if yes, how much and how often? And what if I need him outside office hours?

As a reference point, per local advice I did tip my drivers in India and Indonesia, with a little extra if they had to stay late (going to restaurants after work etc).