A thermal therapy device can be operated for both cold and hot water circulation by using a self-priming pump and four solenoid valves with the open/closed states selectively controlled by an MCU to pump chilled water or cold water from two different water containers to sequentially circulate through two different water paths to a water bladder for cold therapy treatment or hot therapy treatment. During the hot therapy treatment, a water heater is used to heat the cold water until a configured temperature is reached. A pneumatic pump is also employed to carry out an air pressure control mode to pump air into an air bladder securely attached on the water bladder to put pressure on the water bladder for a pressurized treatment. Water retained in the water bladder can also be evacuated and returned to the two different water containers to avoid moss generation and stinky odor.