Parts of Thailand are battling record floods, which have killed at least33 people and prompted authorities to deploy military ships and helicopters to support relief efforts.

The deluge has hit ten provinces across the country's south over the past week, with the city of Hat Yai, a business hub bordering Malaysia, recording its heaviest rainfall in 300 years - 335mm in a single day.

Photos show vehicles and houses submerged in the city, while desperate residents await rescue on their rooftops.

Relentless rains have also ravaged neighbouring countries. In Vietnam, the death toll has risen to 98 in a week, while in Malaysia, more than 19,000 people have been forced from their homes.

More than 2 million people in Thailand have been affected by the floods, but just 13,000 have been moved to shelters.

The vast majority are cut off and unable to get help, according to Reuters news agency.

The Thai military, which has been put in charge of tackling the crisis, said it is preparing to dispatch an aircraft carrier and a flotilla of 14 boats loaded with relief supplies, along with field kitchens that are said to be able to deliver 3,000 meals a day.

Medical teams on board the aircraft carrier will convert it into a "floating hospital" if required, the navy said.

Boats, high-clearance trucks, and jet skis have also been deployed to evacuate residents, said the governor of Songkhla province, where Hat Yai is located.

The cabinet on Tuesday declared Songkhla a disaster zone, freeing up funds for relief.

However, many people remain stranded amid the rising waters.

A volunteer rescue group, the Matchima Rescue Center, told Reuters it had been inundated with thousands of calls in the last three days, with people asking to be evacuated.

People have also posted urgent calls for help on Matchima's Facebook page. "Many people are trapped... Please help," one user wrote. "It's very difficult right now. The water has reached the second floor, where there are children, the elderly, the sick, and the disabled!!!"

Another wrote that his household had been waiting for help for three days: "Every second is crucial now... Please help share. My [phone's] battery is at 40%. Thank you everyone."

Some also wrote about not having had any food and water for days.

A clip that has gone viral on social media shows three young boys hanging from power lines, trying to inch their way to safety while brown murky waters continue to rise below them.

In Malaysia, more than 19,000 people have been evacuated to safety, with 126 evacuation centres set up in the northern border areas.

In the states of Kelantan and Perlis, rescue teams waded through knee-deep floodwaters to evacuate residents in areas where rising waters had cut off access to roads.