To travel to Bandorban pick season is winter. This time weather will be suitable. You won't have to suffer from hot and humid weather. And my suggestion will be to go to Bandarban, best time is rainy season. Does it make you surprise? I know this time hilly roads will be dangerous. Sometimes those will be broken or sleepy. It might be rain while you go out. But still the main attraction of this hill area is to see clouds. You will see several stages of clouds moving around you. You will see clouds are making rain far away, then coming towards you, make you wet and then go away. Every single moment view will be changed. Don't miss it.