My thermostat is located next to the return. This area stays at the right temperature. My bathroom and bedroom can become very hot. Can a second thermostat be added to keep these 2 rooms from getting too hot?

You could add a second thermostat but then you will also have to add a power damper to make the thermostat work. Best solution is to see if there are dampers on the duct work leading to those rooms and adjust if possible.