BANGKOK: Floodwater encircled two industrial estates in the east of Bangkok on Monday and disrupted bus services in the Thai capital, although mass transit train systems were still running and central commercial districts remained dry.

Starting in the north and northeast of the country in late July, the water has slowly moved south, overwhelming industrialised provinces and rice areas in the centre and moving slowly into Bangkok over the past three weeks.

Somkid Tanwatanakul, deputy governor of the Industrial Estate Authority of Thailand (IEAT), told Reuters floodwater had reached the vicinity of the Lat Krabang Industrial Estate but the situation inside the zone was “still normal”.

“The water has surrounded the complex over the past few days with a level now as high as 1.4-1.5 metres,” Somkid said.

“We have strengthened dikes around the estate to 2.60 metres high. My worry is if this much water continues to hold for a long time with nowhere to go, the estate might not make it.”

The estate, which is 10 kilometres north of Bangkok's main Suvarnabhumi airport, covers nearly 1,040 acres and employs almost 50,000 workers in 254 factories making car parts, electrical appliances, food and beverage.

Among the international firms there are consumer goods giant Unilever Pcl, Johnson & Johnson , Isuzu Motors and Honda Motor Co .

It was a similar picture at the Bang Chan estate nearby.

“Our factory is still dry but outside, it isn't,” Yaowaret Kanjanachotkamol, a marketing manager at President Bakery Pcl, said. “We have started to see water in some parts of the estate.”

The government's flood crisis centre said residents of 11 districts in Bangkok had been told to evacuate and partial evacuation zones had been declared in another seven.But it said its use of so-called Big Bags — huge sandbags weighing 2.5 tonnes — to build a protective wall 18 kilometres long across the north of the city appeared to have been successful in reducing flows into the inner city along the first six kilometres constructed.

Weekend market open

The government said 506 people have been killed and 25 of the country's 77 provinces are currently affected.

The Chatuchak district in northern Bangkok was among the latest to be issued with an evacuation order as floodwater moved in over the weekend, although its huge market, popular with tourists and locals alike, remained open.

The overhead Skytrain, whose northern terminus is by the market, is running normally, as is the underground MRT system, which goes through the area.

But many poorer residents rely on buses to get around and they were having more trouble.

Saitarn Siriatcharanon, 56, told Reuters Television she had been struggling for six hours to reach her son in the flooded area, whereas normally the same journey would take 30 minutes.

Bangkok Mass Transportation announced the suspension of bus services in the flooded areas, with military trucks offering an alternative in places.

“I think it will take at least a month for the situation to get better,” said student Tanida Aupornrungrat, a view shared by the authorities, who are having to import pumps to help.

Floodwater is heading towards Victory Monument, where many buses leave Bangkok for other towns. Rama II Road, a major highway to the rubber-producing south of the country, which has not been affected by the floods so far, is also threatened.