Hi there..I can understand your concern for your father. Looks like he suffering from acute gastroenteritis. In this condition it is important to keep him well hydrated(ask him to take plenty of fluids like water, coconut water, ORS solution) and provide only home food(more of curd rice). Start him on probiotics like capsule vibact, twice daily after food, for 5 days. If the condition doesn't improve in two days or it gets worse, kindly consult a general physician for further evaluation. He might need oral antibiotics.