You should never use a microwave for thawing frozen rodents. Microwave radiation actually cooks the rodent from the inside out. Even at the lowest setting a small degree of their internal tissue becomes cooked "meat".

A reptiles stomach is not designed to process cooked meats and you could end up with an undigestable mass rotting inside of your snake.

Thawing with warm water, in the refrigerator, or on a counter in a brown paper bag are much safer ways of thawing prey for your animal.

-adam