At least 58 people are thought to have died in landslides in south-east Bangladesh and in Burma.
Heavy rain caused mudbanks to collapse, burying houses and blocking main roads. Dozens of people are missing, authorities say.
In Bangladesh, most of the deaths have occurred in the beach resort of Cox's Bazar. Five deaths have been reported from neighbouring Banderban district.
Banderban police chief Kamrul Ahsan told the BBC that "four members of a family living in a single house along the hill were entombed by a landslide in the early morning".
Rescue operations are continuing but rains are hampering efforts. Cox's Bazar police chief Nibhas Chandra says it has been raining continuously for the past two days in the area.
Officials say thousands of people are trapped by the floods and that the toll is likely to go up. More rain is forecast too.
Mudslides are common during the rainy season in Bangladesh. The country has more than 200 rivers and is prone to severe flooding.