Rescue workers are reinforcing makeshift walls and sandbags around Bangkok as the worst floods in half a century threaten Thailand's low-lying capital after swamping entire villages in the north.
Floods have covered a third of the country since July, killing at least 289 people and causing about billions of baht in damage.
Prime Minister Yingluck Shinawatra has sought to reassure Bangkok's 12 million people they should largely escape the flooding, Reuters reports.
But Bangkok -- much of it only 2m above sea level -- is at risk as water overflows from reservoirs in the north, swelling the Chao Phraya river that winds through the capital.
High estuary tides are expected to hamper the river's flow into the sea.
However, the governor of Bangkok said in a statement the authorities were preparing an evacuation plan if floods hit the capital, the ABC reports.
Bangkok residents have been stocking up on bottled water and foodstuffs.
The damage from the flooding over the past three months is estimated to have cost at least $US3.2 billion.
Bangkok alone accounts for 41% of the Thai economy and contains heavy industry as well as extensive service, banking and tourist sectors.
At least three big industrial estates in the central province of Ayutthaya have shut temporarily.
Honda Motor Co Ltd said on Friday its plant there, accounting for 4.7% of its global output, will stay closed until October 21.