Dhaka is 4 hours behind Melbourne
Best overlap: 12:00 PM to 6:00 PM in Melbourne is 8:00 AM to 2:00 PM in Dhaka.
The best time to meet is 12:00 PM to 6:00 PM in Melbourne, which is 8:00 AM to 2:00 PM in Dhaka. 6 hours of shared hours is more than enough — slot meetings wherever they're most convenient for the people involved. A quick caveat — Melbourne's clocks move for daylight saving and Dhaka's don't, so the times here are right for only part of the year.