I have a stand up freezer in a closet and I have to leave the doors open all the time for the heat to escape. I have an outside wall and I am thinking of installing a bathroom exhaust fan to vent out, can I install a thermostat and what type would it have to be?
Thanks
Jim

You would need a 120 volt line voltage rated cooling thermostat, one that closes on temperature rise.

See, for example:

COLUMBUS ELECTRIC Thermostat, Attic Fan - Line Voltage Thermostats - 2E340|1A22-7 - Grainger Industrial Supply