They sell everything from noodle soup to sex toys, but Bangkok's famed street hawkers are now facing a crackdown as authorities in the fast-growing metropolis struggle to make space for pedestrians on the crowded pavements.

The move to relocate thousands of sellers from main roads to side streets or restrict touting to the night is part of a campaign to "reclaim the sidewalks" that comes as the ruling junta vows to "clean-up" Thailand's image.

Bangkok residents have long shared their streets with merchants, relying on them for cheap meals and household goods, while tourists are readily found haggling over knock-off handbags, T-shirts or cut-price DVDs.

The stalls that festoon many streets have come to define one of Southeast Asia's most vibrant cities, but are also prompting complaints from some Thais who decry them as hazards -- raising questions over how the bustling capital uses its public space.

"We must return most sidewalks to the people," said Police Major General Vichai Sangparpai, claiming vendors had colonised around a dozen of the city's main roads, obstructing people and traffic as well as damaging the environment.

Action to tackle the congestion has gained momentum since Thailand's generals seized power last May, cracking down on activities including gambling and drug-use in a mission to "restore order" to the nation.

Operations are already underway to evict hawkers from cluttered beaches in tourist hotspots such as Phuket.

But, for the most part, Bangkok's vendors "will be allowed to sell" if they shift to designated zones or stop selling at peak hours, according to Vichai.

- Dividing the city -

Pouring cups of instant coffee from his cart, Mongkol Moradokpermpun said he is one of 3,000 vendors at Khlong Thom market, in Bangkok's historic heart, who have been given until March 1 to relocate several kilometres away.

The 59-year-old, who has sold drinks at the same spot for three decades, is worried about the cost of commuting to the new site.

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"If they don't change their mind, thousands of people will suffer. It will affect our business. Every family will have problems," he said.

It is a common view at the areas being targeted.

In downtown Silom, noodle-seller Juttigan Jitcham told AFP the new ban on daytime sales has halved her income.

"I can no longer pay school fees for my children," the 30-year-old said as she dished up steaming bowls of noodles to evening customers.

Apart from congestion, the crackdown is also taking aim at the criminal networks -- and graft-prone officials -- that have flourished in-step with the mushrooming number of vendors.

A Thai army officer was charged last July with extorting money from salesmen in the seedy Patpong area, a wedge of go-go bars and stalls popular with tourists.

According to Bangkok's town hall, there are 20,000 registered vendors, but thousands more operate without a permit in a nation where a sprawling informal sector accounts for Thailand's remarkably low unemployment rate.

A government survey in 2000 found up to 400,000 people touted goods on the capital's streets, a number thought to have risen with growing numbers of middle-class vendors joining the ranks of lower-income sellers, many of whom have migrated from Thailand's poorer northeast.

- Public backlash -

Narumol Nirathron, an academic from the Social Administration department of Thammasat University, says while curbs are needed to control overcrowding authorities need a broader plan to address vendors' needs.

"I am worried about the effect on the poor who depend on street vending for their livelihood," she said. "The pavement is not only for the pedestrian but it's for the people to earn their living also."

Roadside sellers bind different elements of Bangkok, a capital with a large and widening wealth gap, by bringing together street food patrons from all parts of society and injecting energy and colour into the city.

But they are also facing a growing public backlash.

A Facebook page campaigning for the rights of pedestrians in Bangkok has more than 8,000 'likes' and is full of angry posts blaming vendors for monopolising sidewalks.

Some instead laud Singapore's model for retaining budget food with efficiency by relocating traders during the 1980s to dedicated hawker centres.

Yet Narumol thinks Bangkok could never go as far to de-clutter its streets. "It's too integral a part of Thai life," she said.

In recent weeks, authorities have wrestled back control of sidewalks in parts of the city by demarcating pitches with freshly painted yellow lines.

But long-time hawkers say it will not be long before the stalls are once again unfettered.

Observing police officers speaking to vendors opposite his patch in Khlong Thom, a merchant, who asked to stay unnamed, predicted the crackdown will soon ease.

"Authorities will come and we will hide. When they leave, we will come out to sell again," he said.