Fourteen people have been rescued alive so far since the boat capsized last week near Thailand's Tarutao island while trying to reach Malaysia.

Officials said the vessel was carrying some 70 undocumented migrants, mostly from Myanmar's persecuted Rohingya community.

As the search and rescue operation resumed on Wednesday amid rough seas and rain, Malaysia's Home Minister Saifuddin Nasution Ismail said: "Our main focus now is to find those who are still alive. The priority is to save lives first, every life is precious."

He said the search would continue for a reasonable period, without giving a precise timeline.

Malaysian authorities had earlier said the operation was expected to last seven days.

Romli Mustafa, director of the Malaysian Maritime Enforcement Agency in the northern states of Kedah and Perlis, told AFP that teams involved in the effort around the island resort of Langkawi "recovered five more bodies in Malaysian waters" on Wednesday.

This has taken the overall toll to 32 bodies, including seven found by Thai rescuers in recent days.

The 14 survivors, mainly Rohingya and Bangladeshi citizens, have all been found in Malaysian waters since rescue operations started on Saturday.

At least 12 vessels were searching an area of around 250 square nautical miles, roughly the same size as the city-state of Singapore.

Muhd Azham Azmi, a fisherman in Langkawi, told journalists on Tuesday how he had helped rescue a survivor, after initially mistaking her for "red floating debris".

"When my friends and I got closer, it turned out to be a woman clinging to two planks," an animated Azham said, recalling the Saturday rescue.

"She only moved when we steered closer to her. That's when we realised she was a person! We panicked... we'd never seen anyone floating in the sea like that before."

The woman was quickly lifted onto the boat and given some water and cake, added the 34-year-old fisherman.

"We couldn't understand her language. She used hand gestures to ask us to bring her ashore."

The passengers on the capsized boat were likely part of a larger group of some 300 people who had left Myanmar two weeks ago, and were split between at least two vessels, officials say.

Malaysian police reported the second vessel as missing.

Relatively affluent Malaysia is home to millions of migrants from poorer parts of Asia, many of them undocumented, working in industries including construction and agriculture.

But sea crossings, facilitated by human trafficking syndicates, are hazardous and often lead to overloaded boats capsizing.

The Rohingya have been persecuted in Myanmar for decades, and thousands risk their lives every year to flee repression and civil war, often aboard makeshift boats.

As authorities continue to scour the waters around Langkawi, Azham said he hopes that "those who are still missing... are still alive."