The death toll from floods in southern Thailand has risen to 36 with at least one major hospital, an airport and several highways still closed.

One of the latest casualties was a 54-year-old electrician and father of three who took his own life after the waters destroyed most of his possessions in Bang Saphan district.

"He was stressed because of the flood, this is the first time in 50 years such a severe flood happened here in Bang Saphan district," said Chaiyanit Tonsap, a friend who waited at a makeshift hospital in a school hall.

It is not clear if the suicide was counted in the Government's official death toll.

With local temples flooded, the family decided to drive through the night and return the man's body back to his hometown.

"The flood has not only caused medical conditions [but] it has also effected the psycho-social [outlook] for our patients," volunteer doctor Yanin Nokdhes told the ABC.

Ms Yanin travelled from Ayutthaya, 450 kilometres away, to help set up a temporary field hospital which treated about 100 patients on Tuesday and Wednesday.

"We are trying to help each other hand by hand and together … we are going to make this better," she said.

"Some of them are new patients, like dog bites, lacerations from walking in the water and there are some patients that [were being] treated at another hospital which got caught in the flood so they send the patients to us."

While some tourists have been inconvenienced in the floods, the real damage is to roads and businesses. ( AP: Adam Schreck )

Clean-up begins

The rain has eased in some parts of the south and the water is starting to recede, allowing a major clean-up to get underway.

The Thai Government estimates that 43,000 businesses have been affected, while 19 highways were impassable.

Sections of the north-south rail line have buckled under the pressure of floodwater and the Nakhon Si Thammarat airport remains closed.

The Bang Saphan hospital had to close and relocate patients after being by swamped by water a metre deep, destroying an x-ray machine and dental equipment.

Young members of the Royal Thai Air Force helped staff pump out flooded sections, hose down muddy furniture and remove debris.

"It is the worst flood in [the] hospital's history, a 60-year-old patient told us she's never seen it this bad," said Cherdchai Chayawatto, doctor at Bang Saphan Hospital.

A small boat was needed to get to staff residences at the back of the hospital compound.

The part of southern Thailand that has seen the worst flooding is a departure point for the popular resort islands of Koh Samui, Koh Phangan and Koh Tao.

While some foreign tourists have been inconvenienced, the real damage is to roads and businesses.

January is typically the driest month in Thailand, but this unseasonal deluge may not be over yet, with weather forecasters predicting more heavy rain will hit the south on Sunday.