A pregnant woman gave birth in the back of a truck as rescuers rushed her to a hospital during severe floods in southern Thailand.

The mother-to-be and two other heavily pregnant women were saved from their submerged homes in Songkhla province on November 27.

But during the 50-kilometre (31 miles) journey to Songkhla Hospital, she went into sudden labour while their truck was caught in traffic chaos for more than an hour.

More rescue workers were dispatched to clear the road as they battled to rush the woman to the hospital in time.

Dramatic footage shows volunteers dashing along the clogged highway, frantically waving for drivers to make way. Lead vehicles were also deployed to part the sea of cars ahead.

Despite their efforts, the woman gave birth just two kilometres (one mile) away from the hospital. Nurses onboard helped deliver the newborn safely.

Nittaya Harasuk and Sarawut Boonsang said they were glad to have successfully delivered the baby girl. They thanked officials for helping clear the way, allowing them to reach the hospital amid the traffic jam caused by widespread floods.

Upon arrival, medics rushed the newborn and her mother for treatment, while the other two women immediately went into labour.

The death toll is expected to breach 100 as catastrophic floods, described by Prime Minister Anutin Charnvirakul as 'the worst flooding in 15 years', swept through southern Thailand.

Police Lieutenant General Trairong Phiewphan, Deputy Inspector General of the Royal Thai Police, said 104 deceased victims have been sent for identification on Thursday evening.

Soldiers, volunteers, and local government units have also been mobilised to hasten relief efforts, but they were hobbled by limited phone signal in the area.

The Thai military has sent some 200 boats, 20 helicopters and its lone aircraft carrier, the Chakri Naruebet, to deliver essential supplies and carry out rescue efforts.

Songkhla's Hat Yai district was among the worst-hit areas, which saw a record 13 inches (335 mm) of rain in a single day on November 21.

Songkhla Governor Ratthasart Chidchoo on Monday declared all 16 districts disaster zones and ordered the immediate evacuation of children, the elderly and the sick.

On Sunday, high-clearance trucks arrived to evacuate more than 400 tourists from flooded hotels across the city.

The Disaster Prevention and Mitigation Department said that floods hit nine southern provinces, affecting some 1,128,284 households and 3,221,958 people.

The Southern Eastern Meteorological Centre said a strong monsoon trough was causing the heavy rainfall, which was expected to ease this week.

Thailand and neighbouring countries in Southeast Asia are in their annual monsoon rainy season which sees soaring temperatures followed by powerful rain storms in the afternoon leading to widespread flash floods.