If you're in Dhaka International Airport(DAC) or have plan to visit Bangladesh while you're in a journey, Bangladesh has offered landing permit visa or instant land permit facility at DAC. So, you don't need to be worry for entry permit to
Bangladesh, it's ready to welcome you anytime if you're from a supported country of current list. Please check
this link to be sure of landing visa. However you can contact the immigration if your country not available in this list.