BANGKOK -- The death toll from Thailand's worst floods in half a century climbed past 500 Sunday, as advancing pools of polluted black water threatened Bangkok's subway system and new evacuations were ordered in the sprawling capital.
The latest district added to the government's evacuation list was Chatuchak, home to major public park and an outdoor shopping zone that is a major tourist attraction. The Chatuchak Weekend Market was open but missing many vendors and customers Sunday as floodwaters poured past the market's eastern edge for a second day.
So far, Bangkok Gov. Sukhumbhand Paribatra has ordered evacuations in 11 of Bangkok's 50 districts, and partial evacuations apply in seven more.
The evacuations are not mandatory, and most people are staying to protect homes and businesses. But the orders illustrate how far flooding has progressed into the city and how powerless the government has been to stop it.
Chatuchak is just a few miles (kilometers) north of Bangkok's central business district, which still is dry. On Sunday, cars sloshed through a flooded road underneath Chatuchak's Mo Chit Skytrain station, the northernmost stop on Bangkok's elevated train system.
Floodwaters also reached roads at three subway stops in northern Bangkok, though both mass transit networks are functioning normally.
Relentless rainfall has pummeled vast swaths of Thailand since late July, swamping the country and killing 506 people, according to the latest government statistics. Most victims have drowned, while a handful died from flood-related electrocutions.
No deaths have been reported in Bangkok. The nearby province of Ayutthaya, which has been submerged for more than one month, has the highest toll with 90 reported dead.
Floodwaters have begun receding in some provinces north of the capital, and a major cleanup is planned in Ayutthaya this week. But the runoff has massed around Bangkok and completely submerged some of the city's outer neighborhoods.
Also in Chatuchak, water has begun approaching a main road near the Mo Chit bus terminal, a major gateway to northern Thailand. The bus station and roads in the area remained open, traffic police chief Uthaiwan Kaewsa-ard said.
In the last few days, floods have also begun moving southward in adjacent Lad Phrao, a district studded with office towers, condominiums and a popular shopping mall.
On Friday, workers completed a 3.7-mile (6-kilometer) flood wall made from massive, hastily assembled sandbags to divert some of the water flowing toward central Bangkok. But large amounts of water are already beyond that wall, and officials say that besides a network of canals and underground drainage tunnels, there are no more barriers preventing water from pushing south into the heart of the city.
Over the past two decades, Bangkok's much enlarged and improved drainage system has increasingly been able to siphon off water during monsoon seasons with average rainfall. But amid Thailand's worst flooding since World War II, that system is facing its greatest test yet.
Prime Minister Yingluck Shinawatra says a plan to be put before the Cabinet on Tuesday would allocate 100 billion baht ($3.3 billion) for post-flood reconstruction.
Yingluck's government has come under fire for failing to predict the threat to the capital. Residents also have been frustrated by widely different assessments of the flooding situation from the prime minister, Bangkok's governor and the country's top water experts and officials.