Where travellers once queued for flights to exotic destinations, hundreds of tents in a Bangkok airport are now shelter for families who fled a torrent of floodwater.

A disused terminal building in the capital's second-largest airport, Don Mueang, has been opened up for 1,500 flood victims, some of whom recounted fearing for their lives as they escaped the rising waters.

"My husband and I fled death," said Nonglak Yodnankham from nearby Pathum Thani province, describing how the mass of brown water swelled at a terrifying pace.

"Within five minutes, it came up to my waist already," the 33-year-old told AFP at the airport, which now serves mostly domestic destinations since the opening of the modern new international gateway east of Bangkok in 2006.

Wannee Chaasamrong, also from Pathum Thani, said she had to swim through water up to her chin to rescue her belongings before escaping.

"Even the army in the area cannot control the water. Six barriers collapsed. The water didn't stop rising. Some people were waiting and staying on roofs. They wanted to leave but the boats were too small," she said.

Chunjit Panjanuwat, a government coordinator at the airport shelter, said it was key to reassure distressed families they were safe after their ordeal.

"The most difficult thing is dealing with people's emotions when they arrive. We have to reassure them so they will trust us to find them somewhere to stay and food to eat."

Three months of unusually heavy monsoon rains have killed more than 340 people across the country, damaged properties and livelihoods and forced tens of thousands to seek refuge in shelters.

Winai Kotbaan, 29, said he carried her parents through chest-deep water from the third floor to get to safety.

"My dad has to walk with a walking stick. I still have to go to work because now I am the only breadwinner," she added.

Inside the former departures hall, volunteers handed out free meals and water to elderly people sitting in front of their green, red or blue tents, while in the children's corner youngsters crafted paper airplanes.

Elsewhere, teenage girls huddled together charging their mobile phones and gossiping over magazines.

Chunjit said some 700 tents had been erected on the groundfloor and the centre was not yet at full capacity.

"The shelter can handle 2,000 evacuees with tents and 3,000 without tents," she said.

Despite the close proximity of the living quarters and the occasional complaint about having to wait in line for the bathroom, the atmosphere appeared calm and relaxed.

"We console one another. We understand one another because we all faced a natural disaster," said Wannee.

While the authorities have reinforced flood barriers around the airport, areas nearby were already starting to be submerged, raising doubts about how long the shelter would remain a safe haven.

The refuge has opened its doors not just to flood-affected men, women and children -- dozens of families have brought their dogs along, setting up camp outside the terminal to allow the animals to run free.

Not everyone at the shelter was comfortable sharing a space with man's best friend, and it was not an arrangement coordinator Chunjit wished to encourage.

"I understand that some people want to rescue their dogs first but they misunderstood and came here thinking we were dogs-sitters," she said.