Heavy monsoon rain overwhelmed parts of Thailand, Malaysia and Indonesia this week, killing more than 300 people and leaving thousands stranded, many on rooftops awaiting rescue.

On Friday, rescuers in Indonesia were struggling to reach the worst-affected areas of Sumatra island, while workers at a hospital in southern Thailand moved bodies into refrigerated trucks after the morgue exceeded capacity.

The water level reached three metres (9.8 feet) in southern Thailand's Songkhla province and killed at least 145 people in one of the worst floods in a decade.

Prime Minister Anutin Charnvirakul visited a shelter for evacuees in hard-hit Hat Yai district on Friday.

"I really have to apologise to them for letting this happen during the time I am in government," he told reporters in footage broadcast on AmarinTV.

"The next step is to prevent the situation from deteriorating," he added, announcing a two-week timeframe for the district's cleanup.

The Thai government rolled out relief measures for those affected by the flooding, including compensation of up to two million baht ($62,000) for households that lost family members.

- Public criticism -

As floodwaters receded, shop owner Rachane Remsringam picked through rubbish strewn between the aisles of his general goods store, lamenting hundreds of thousands of dollars in losses.

His store, Madam Yong, was looted and vandalised in the wake of the disaster, he said.

There has been growing public criticism of Thailand's flooding response and two local officials have been suspended over their alleged failures.

An MP from the opposition People's Party criticised the administration, saying it "wrongly estimated the situation" and made "errors in handling the flood crisis."

Officials on Indonesia's Sumatra said flooding and landslides this week had killed at least 174 people, with nearly 80 more missing.

Two people were killed in Malaysia by flooding caused by heavy rain that left stretches of northern Perlis state under water.

The annual monsoon season, typically between June and September, often brings heavy rain, triggering landslides and flash floods.

A tropical storm has exacerbated conditions, and the tolls in Indonesia and Thailand rank among the highest in flooding events in those countries in recent years.

Climate change has affected storm patterns, including the duration and intensity of the season, leading to heavier rainfall, flash flooding and stronger wind gusts.

A warmer climate holds more moisture, producing more intense rain events, while warmer oceans can turbocharge the strength of storm systems.

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