Thailand Prime Minister Yingluck Shinawatra is calling for all political factions to unite as soldiers and workers struggle to shore up dikes protecting Bangkok against raging floodwaters.

Hundreds of soldiers and volunteers heaped sandbags into breaches in dikes protecting industrial and housing estates north of the capital Wednesday. A government warning identified several districts that could be inundated because of “complications” in the operation of the dikes.

An army lieutenant warned that a sewage treatment pond in one estate was threatened.

He said if the pond is flooded, the sewage will flow into the factories.

Ms. Yingluck toured affected areas by helicopter Wednesday, and afterward told reporters she cannot handle the crisis by herself. She urged opposition parties to set aside politics and cooperate with her government to restore people's morale.

Former Prime Minister Abhisit Vejjajiva, who was defeated by Ms. Yingluck this year, did not respond directly to her appeal, but he warned that the capital is still at risk from the nation's worst flooding in 50 years.

Bangkok Governor Sukhumbhand Paribatra had declared the crisis largely over on Monday. But he said Wednesday he is still very worried.

Despite its problems, the government Wednesday announced a donation of almost $100,000 in flood relief for neighboring Cambodia, which has been equally hard-hit. The floods, have also deluged Vietnam, Laos and the Philippines, killing more than 700 people across Southeast Asia.

Ms. Yingluck's government has been working to repair relations with Cambodia following a series of border clashes that killed 28 people this year.