Myanmar's president called for the evacuation of low-lying areas on Thursday as the Irrawaddy river threatened to breach embankments.
This left the villagers with just sand bags to hold back churning waters that have hit much of the country.
Floods from heavy monsoons have cut through swathes of South and Southeast Asia in recent weeks, claiming hundreds of lives and displacing millions.
Twelve of Myanmar's 14 regions have been struck, with officials saying 74 people have been killed and more than 330,000 affected -- many forced into monasteries and other makeshift shelters after their homes were inundated.In a picture muddied by damaged communications, relief agencies said floods had receded in some northern and western areas allowing supplies of food and clean water to trickle in, although landslides were still a threat.
Parts of the centre and south, Myanmar's main major rice-growing area, are now bracing for floods as water drains through the vast Irrawaddy delta.
In a radio broadcast repeated throughout Thursday, President Thein Sein said areas near the Irrawaddy were at risk as the river rises "above danger level".
"As we cannot prevent natural disasters, I urge fellow citizens to move to safer places... it's the best way," he said, adding Hinthada and Nyaung Don townships along the river were in immediate danger.
Nervously watching the river
That message was already too late for some villages around Hinthada, where waters had reached the height of doorways and residents now navigate their flooded streets by canoe.
In the main town, which is yet to be swamped by the dirty waters, the army helped residents reinforce embankments with sand bags as displaced people arrived seeking shelter in monasteries and schools.
But the swollen river lies menacingly close on the other side of the barriers, an AFP reporter said.
Upstream at Nyaung Don, sand bags were piled high along the river as villagers anxiously eyed the rising waters.
"We are not sleeping at night, instead we watch the embankment and hope it does not break," said 23-year-old Tun Tun.
International aid efforts have buttressed the response of the army and local communities, following a rare appeal by the government for outside help.
But thousands of people are still feared stranded in rugged and remote Chin State after days of rain caused flash floods and landslides that swept away homes, roads and bridges.
Further south, aid agencies have warned water sources have been contaminated in parts of Rakhine State, which was also hit by Cyclone Komen late last week.
The floods have heaped further misery on the state, which already has tens of thousands of people in displacement camps -- mainly Muslim Rohingya -- after waves of sectarian violence.
Concerns over food security are also mounting as the UN said more than one million acres of farmland have been flooded, devastating the staple rice crop.
Suu Kyi plea
Myanmar is set for a general election in November and the floods have taken on a political dimension, with both the quasi-civilian government and opposition -- led by Aung San Suu Kyi -- at pains to show they are reacting speedily to the floods.
The government's embrace of foreign help is in stark contrast to the former ruling generals, who refused assistance for weeks after the 2008 Cyclone Nargis, which left 140,000 dead or missing.
In a video message on her Facebook page, Aung San Suu Kyi said her already impoverished country will need international help long after the floods recede.
But she also warned of the dangers of the disaster being used as a "reason for upsetting" the election, citing a controversial referendum driven through by the former junta days after Nargis struck.
India and Pakistan have faced the worst of this year's monsoon with hundreds dead and more than two million displaced across the two nations.
More than two dozen people died late Tuesday in central India when a flash flood derailed two passenger trains.
Vietnam and Nepal have also seen scores killed.