It is almost two in the afternoon and the lunch-hour crowd has thinned, but medical technologist Natnicha Muangsisan is just taking her break.

She heads to Convent Road, just around the corner from Silom, which is often called Bangkok's Wall Street.

"I have different break times, so street food is very convenient for me," Ms Natnicha, 31, tells The Sunday Times, as she looks at the food stalls lining the pavement, selling noodles and rice dishes.

"Street food is cheaper than restaurant food, and eating in restaurants can be more expensive but not necessarily delicious."

In Bangkok, street-food vendors offer meals for as low as 40 baht (about S$1.60) at all times of the day and night, and are a hit with locals and tourists. But there are concerns that street-food vendors may become more elusive in the wake of a drive since last year by the Bangkok Metropolitan Administration (BMA) to sweep these vendors off major roads.

Those selling clothes, souvenirs and other knick-knacks have also been cleared from Siam Square, Pratunam, Ratchaprasong and Sukhumvit.

Next to be tidied up: tourist haunts Yaowarat in Chinatown and backpackers' alley Khao San Road.

"The intention is to set order in Yaowarat and Khao San Road. It is not about banning street-food vendors," Dr Vallop Suwandee, BMA chief adviser, tells The Sunday Times.

News last week that the authorities were planning to rid Bangkok's streets of its vendors caused outrage, but Dr Vallop has said he was misunderstood.

The city wants to regulate and zone its hawkers, not deprive them of their livelihood.

For a start, BMA plans to set up zones where vendors can park their pushcarts and set up makeshift tables on Yaowarat's pavements.

They will also dedicate lanes for tourists to walk without obstructing traffic or causing accidents.

"We do realise that these two areas are tourist attractions, but in order to make tourism sustainable, the city has to step in and look at the problems," Dr Vallop says.

Traffic congestion, he adds, is the main problem in Yaowarat, the main road that runs about 1.5 km across Chinatown.

The five-lane road is reduced to three lanes in the evenings to accommodate vendors and pedestrians, causing traffic congestion.

Dr Vallop says the problem is not as severe in Khao San Road, which is just 300m long and is more manageable.

Since last month, vendors have been meeting the government to discuss solutions.

Traffic woes are not the only issue. BMA wants vendors to print their menus and display prices clearly to prevent customers from being scammed.

It also wants to impose strict standards on sanitation, including how vendors cook food, wash dishes and dispose of trash.

"In the past, vendors would throw their rubbish on the ground, but the government has emphasised that it is our responsibility to dispose of them properly," says Ms Nipha Pinitwikan, 38, who sells fish maw soup in Yaowarat.

BMA has cited complaints about rat infestation and stench coming from the drains due to careless disposal of rubbish, not to mention the waste clogging waterways, causing floods during the rainy season.

Ms Nipha says vendors are receptive to BMA's sanitation requirements because they want to keep their livelihood.

Still, other vendors remain jittery, including Mr Wisut Saejong, who has been running a noodle stall in Convent Road since he was 15.

"This is the only livelihood I know," says Mr Wisut, now 40.

"If they move me to another spot, it's OK but I'm not sure if my customers will follow."

Dr Vallop says food vendors at Yaowarat and Khao San can continue to make a living there, as long as they follow BMA regulations and meet requirements, including health checks twice a year.

They will also need to attend an orientation programme to get certification. The regulations apply to vendors in these two areas, but Dr Vallop says vendors elsewhere can sell on minor or side streets for now, as long as they do not pose problems to pedestrians or obstruct vehicular traffic.

The regulations may eventually be rolled out to include them too.

"We cannot designate all areas into food streets, otherwise everything will go back to the same old disaster, which was disorderly," he says.

But Mr Chuchat Chawakut, 44, an office worker in Silom, says food vendors are not the ones causing inconvenience on pavements.

"Those stalls selling other things like clothes... they are the problem," he says.

Still, BMA just wants to control the chaos.

"In New York, would they allow this unregulated business in Fifth Avenue? Or Singapore, in Orchard Road?" Dr Vallop asks.

"The pavement is a public area.

"It has to be shared by everyone concerned and not be taken over by street vendors."