Hi PT.. you can ask for a raise and, instead of firing you he can say no (and tell you what you need to do to get a raise) or he can say yes or he can compromise.
Firing someone who asks for a raise is not professional.
I have been on both sides of this issue FWIW. I have actually talked to employees about more money and what they need to do to GET more money b4 they even ask. I have also handed out raises w/o being asked.
My criteria was based on job performance and what this emplyee was doing to be more efficient, do things better and improve my bottom line.
When asking for a raise, it is important to show your boss why you deserve it (things you have done to improve efficiencey, improve the bottom line, extending yourself thru extra time spent, extra responsibilities taken, not taking time off etc.).
Good luck!