From Shanghai to Kuala Lumpur, one direct flight MU539 operated by China Eastern Airlines is available daily. Flight schedule: Shanghai-Kuala Lumpur, 19:30-00:50. After reaching Kuala Lumpur, you could take a flight to Dhaka directly. Besides, several flights operated by China Southern Airlines on the route Shanghai-Kuala Lumpur-Dhaka are available daily. About the airfare details, you could inquire on the page below with your exact departure date, since the international airfare is various on different travel date.
https://www.travelchinaguide.com/china-flights/cheap-shanghai-flights.htm