BANGKOK - THE worst flooding to hit parts of Thailand in decades has inundated about a quarter of the country, officials said on Wednesday, as the death toll from fast rising waters climbed to 12.

Rescue teams helped evacuate stranded people by boat as homes and huge swathes of farmland have been deluged, while in Bangkok people living on the banks of the Chao Phraya River were braced for overflowing waters.

'The flooding in many provinces remains critical and the water has spread widely, leaving about one fourth of Thailand flooded,' said interior minister Chavarat Charnvirakul.

Four people died in Buriram, in eastern Thailand, as waters gushed through the streets, while the death toll in severely affected Nakhon Ratchasima has risen to four, said an official from the Thai interior ministry.

The central provinces of Rayong and Trat have both reported one casualty, while a further two people were killed in Lopburi.

More residents in Nakhon Ratchasima, where 30 of 32 districts are already under water, were told to evacuate or move to higher ground after a local reservoir burst its banks, an official said.

Thai floods kill 12