Do you have to have a credit card when renting a vehicle from thrifty? Or can you use a debit card?

Yes, credit card is required.

You'll need credit card Just to hold the Car (when you pick it up)but at the end of the rental you can pay with Debit card

Certain companies accept debit cards but only certain locations. Before i had a credit card I called around and found Alamo was helpful at one location but not another.