With no money or identity documents and stranded in a foreign land for days on end without food and water, they are the forgotten people of Thailand's flood disaster.

Evacuation is not an option for hundreds of Burmese migrant workers marooned in the newly formed swamps and road-rivers that cover industrialised central Thailand.

Many are in Thailand illegally, but even the legitimate migrants fear arrest or becoming victims of extortion by Thai and Burmese border officials and opportunist mafia gangs.

We have to take care of ourselves, we share the little food we have, but that's gone, said Show Tae, 34, who worked in a factory making pizza bases before water rushed in a month ago.

We can't go home because we have no money and if I go back to Myanmar, there's no work there either.

In provinces like Ayutthaya, 100 km (65 miles) north of Bangkok, hundreds of Burmese are trying to ride out Thailand's worst floods in half a century, crammed into apartment blocks with no electricity and relying on a few aid groups to navigate submerged roads to deliver food, water and medical supplies.

Homes and shops have been destroyed, industrial estates housing hundreds of factories have been forced to shut down, leaving 650,000 people jobless. More than 400 people have been killed and 2 million affected since July.

People like Show Tae are not the priority as authorities, troops and relief workers battle to reach thousands of Thais cut off by water as deep as two metres in provinces like Ayutthaya, Pathum Thani and Nakhon Sawan.

Many Thais are in evacuation centres, or camped out along highways, sleeping in small tents, the back of parked trucks or under plastic sheets, but food and water is available.

DIRE SITUATION

Families are crammed into boats, rowing along roads and through rice fields with a backdrop of warehouses, tractors and bulldozers partially submerged by the muddy, foul-smelling water that has left this province looking like a coastal area.

For Burmese, the situation is even more dire. Activists say migrant workers hit by floods -- a crucial part of Thailand's $319 billion economy -- have been largely ignored.

They have no one, nowhere to go and the factory owners can't take care of them, said Laddawan Tantivitayapitak of the Thai Action Committee for Democracy in Burma (TACDB), which was delivering food supplies to the Burmese victims on Tuesday.

Many lost their documents and money in the floods. Other chose to flee but were arrested.

About 250 Burmese are believed to be receiving help in shelters, but tens of thousands more were affected by the flooding.

The Labour Ministry estimates there are more than 1 million foreign migrant workers in Bangkok and surrounding provinces, including those who are registered and those working illegally. Those with documentation are not permitted to travel beyond the provinces in which they are employed.

For many, evacuation means detention or the possibility of being delayed or blocked from returning to jobs in Thailand that help feed millions of impoverished people back in Myanmar.

Many have decided to go home anyway. Activists say thousands of labourers have escaped swamped areas and have been cramming into trucks, forced to part with about 2,500 baht ($81) to get to the Thai-Myanmar frontier, where some border officials on either side have been demanding informal fees just to allow them to get home.

It is unacceptable for Thai and Myanmar officials to be profiteering from migrants' desire to go home in a time of disaster like this, said Andy Hall, a migration expert at Bangkok's Mahidol University.

Thailand has not been able to efficiently and humanely provide for affected migrants inside the country so far.

Win, 19, a registered worker at the pizza base factory who was born in Thailand but does not have citizenship, said she and her colleagues were destitute and many living in fear.

We no longer have work but my friends have no choice but to wait, she said. They're too scared to leave.

(Additional reporting by Jutarat Skulpichetrat; Editing by Raju Gopalakrishnan)