Malaysia and Thailand are facing a second wave of heavy rain and potential flooding this week, authorities said on Monday, even as some displaced residents were able to return home and the worst floods in decades began receding in some areas.

There are worries in Malaysia and neighbouring Thailand that disastrous flooding could get worse as more rain comes.

At least 12 people have died and more than 600,000 households have been affected by the worst flooding in southern Thailand in decades, according to a government agency.