When the floodwaters came up to her chin, Karuna Leuangleekpai knew she had to abandon her house on the outskirts of Bangkok. But she had no idea what to do with her seven dogs.

Through Facebook, she heard about a flood evacuation shelter for pets run by veterinary student volunteers in the capital, so she crammed her soaking wet dogs into her car and went to seek help.

"The water was above my head when we left the house -- the dogs were swimming around. That was over a month ago and my house is still underwater," Karuna told AFP.

"I'm glad to have found this shelter for them -- I'm staying with a friend in her apartment but there's no way my dogs could have fitted in too."

Three months of unusually heavy monsoon rains have inundated large swathes of Thailand, killing more than 650 people and affecting the homes and livelihoods of millions.

But it is not just humans who have been suffering during the kingdom's worst floods in half a century -- tens of thousands of pets and stray cats and dogs have also been stranded as water levels rise.

Their plight has prompted an outpouring of sympathy from city residents, who have mobilised using Facebook and Twitter to set up animal shelters, organise "pet rescue" patrols and provide free medical care to flood-hit pets.

"We knew that the floods would make it hard for owners to care for their pets and we felt we had to help," said veterinary student Mataya Taweechart, adding that the animal shelter was set up and run by students and volunteers.

Waters are now receding in many areas, but for people in some of the capital's suburbs, the misery continues and there is little sign that the supposedly-temporary pet shelter will be able to shut soon, she said.

"We are using an abandoned government building, we can't stay long. But some areas of the city are still flooded, so we still have a lot of animals," she told AFP as she bottle-fed a two-day-old kitten.

The shelter in Bangkok's Maen Si district runs on donations of cash and food. The service is free and most people hear about the shelter -- and alert them to cases of abandoned animals -- through Facebook, she said.

Most of the some 500 animals at the shelter have owners, but some -- like the kittens, which were left in a cardboard box outside -- have been abandoned.

The shelter will try and use its online networks to find them new homes, she said.

It is one of dozens of Thai-run shelters set up to help flood-affected animals. They are largely organised online on popular Thai-language forums such as Pantip.com, run by volunteers and funded by donations.

There are also a number of larger state-run centres for pets -- managed by the government's Livestock Department -- which are caring for thousands of animals, Chutipon Sirimongkolrat, a vet from the department told AFP.

More than 7,000 animals have passed through the department's four centres, he said -- mostly dogs and cats, although they have also had a fair number of rabbits, mice, birds, three goats and even an iguana.

More than 5,000 animals are still at the shelter, but the department is no longer accepting new arrivals and is urging owners to collect their pets as soon as possible.

"We're trying to clear all the animals we have in our shelter before Christmas," he said, adding that it was hard to estimate how much the shelters cost to run but that they had received generous donations from the public.

The city's handful of regular animal shelters are also packed to capacity, as they look after flood-affected strays and abandoned pets, which are usually brought in by worried members of the public, said local animal charity SCAD.

"We're thinking of the long-term implications of the flood -- it will be well into next year before we are back down to our normal volume of animals," said SCAD operations manager Lindsay Hartley-Backhouse.

SCAD is currently looking after some 70 cats -- they usually have around 20 at any one time -- and hundreds of dogs, with more animals "definitely" on the way, she said.

"In the long term, I think we will end up with a lot of leftovers," she said, adding that the animals would go into SCAD's adoption programme, which posts photographs of potential pets on its website hoping to find them new homes.

The outpouring of sympathy that has helped keep Bangkok's animals safe during the floods looks set to continue and the huge level of interest online may help many abandoned animals find new homes, she said.

"We've had quite a lot of adoptions recently. At first no one came, but now people are really interested -- maybe they realise that they want a pet anyway, and now is a good time to adopt one," she said.