For decades, Soi 38, Bangkok’s famed foodie haunt on Sukhumvit Road, was a carnival of colours, smells and sounds. Nearly every night, woks sizzled and the narrow road overflowed with roving eaters lining their stomachs for long nights out. Under bright yellow lamps, street vendors served stewed pork knuckle, oily chicken rice and plate after plate of piquant pad thai.

But when the owner of this land passed away in 2014, his family sold it to a property development firm and construction of a luxury condominium got underway. Today, instead of the symphony of backpackers, families and young Thai couples filling up at foldable tables, the raspy cry of cranes and backhoes floods the air. While a few vendors remain, the writing is on the wall for this hallowed street food destination.

The demise of Soi 38 isn’t unique. Over the past year, the Bangkok Metropolitan Administration has evicted nearly 15,000 vendors from 39 public areas citywide, part of a campaign to tidy up the streets and pavements. Vendors along the whole of Sukhumvit Road, from Soi 1 to Bang Na, have been told they must vacate by 5 September. Meanwhile, guidebook go-tos, such as the On Nut Night Market, the Saphan Lek Market in the Old Town and the Khlong Thom Market in Chinatown, as well as vendors along Siam, Sathorn and Silom Roads, have all faced the axe over the past two years, a rapidly unfolding consequence of social, economic and environmental pressures.

Cleaning up the city – in particular, relieving its choked traffic by removing rogue vendors from walkways and narrow side streets – has long been a talking point of politicians on the campaign trail. Until the junta seized power in May 2014, however, none had made good on their promises. With military officers given substantial, wide-reaching policing power, while the police themselves also patrol the streets, such edicts now resonate loudly.

In On Nut, a residential neighbourhood popular among expats, a well-loved, ramshackle night market closed in October 2015 when the owner of the land sold the prime property next to Bangkok’s iconic BTS sky train to a developer. As in Thong Lo, a condominium will soon stand in its place. Panida “Poupée” Pethanom, who served gourmet hamburgers from her Burgers and Bangers stall, said she expected the land to be sold eventually, although the two-week eviction notice came as a jolt.

Another top tourist landmark, Pak Khlong Talad, the sprawling riverside warren in the Old Town better known as the Flower Market, has also felt the effects of gentrification. One of the market’s warehouses has been transformed into an as-yet-unfinished community mall called Yodpiman River Walk, with tourist shops, cafes and restaurants. The vendors on the footpath in front of it, who sold vibrant marigolds, roses and orchids, as well as noodles, stewed duck and pork satay, have been evicted. Their wooden tables have been replaced by yellow tents inside of which city inspectors known as tessakij keep vigil, cracking down on rule-breaking vendors with greater gravity than ever before.

“When foreigners hear ‘Flower Market’, they think of beautiful bright colours and lots of activity,” said Sathaporn Kosachan, who, with his partner Suchanat Pa-obsin, sold khanom jeen (rice noodles with curry) at the Flower Market for 20 years. “But now it’s, ‘What is this? Where is the market?’ They expect to see something different from what they can see in Europe or Japan. They want to see the flowers, the food, the vendors, because it’s exotic, but all the vendors have been separated and now many have left.”

Pongphop Songsiriarcha, assistant editor of local lifestyle magazine Bangkok 101 and lifelong resident of the Pak Khlong Talad neighbourhood, has also noticed a loss of diversity on the streets.

“Around the corner from my house, you used to be able to find yam [a tangy, spicy and savoury salad], chicken rice and so much more, but it’s all gone. Even gaeng massaman [a classic Thai curry] is not very easy to find now,” he said.

Less diversity not only means fewer choices for the on-the-go working class, who eat out more often than they cook at home, but it also means that less common dishes – such as pad galamphlee (cabbage stir-fried with fish sauce) and savoury flower-shaped snacks called cho muang – are at risk of disappearing from the streets and fading from public consciousness.

Yet perhaps the greatest loss the city stands to face if its street food scene gentrifies – or vanishes – is its unique coming together of cultures and classes. The street stall is one of few places where businesspersons can mingle with the people who clean toilets and drive taxis. Sitting on the same plastic stools, everyone slurps the same noodle soups with well-worn chopsticks and bent spoons. But if 100-baht food court meals become the cheapest eats available, then the divide between haves and have-nots seems fated to expand, with blue-collar workers effectively priced out.

Food is so tightly woven into the fabric of Thai culture that any threat to it, perceived or actual, tends to elicit powerful emotional responses. But lost among the outcries is one thing that might be street food’s saviour: urban planning, a relatively new concept to Bangkok.

“Street food is Bangkok’s treasure. We cannot lose it,” said Dr Nattapong Punnoi, business development director of the Urban Design & Development Center, a four-year-old organisation launched by Chulalongkorn University that aims to restore and develop urban areas. Punnoi agreed that a number of vendors operate illegally, block footpaths or don’t clean their messes well, compounding the megacity’s litter and pollution problems.

“We need proper planning to implement sustainable changes,” he explained, adding that Bangkok has roughly 28,800 hectares of space that could be sustainably developed: abandoned railyards, unused private land, promising spots hidden beneath highways and overpasses. All could incorporate street food in such a way that connects patrons with the spaces as well as each other.

“Around town, we’re seeing a lot of community malls opening – small malls with restaurants and shops – where you can buy Japanese products and eat Italian food, for example,” Punnoi said. “One of the suggestions we make to these organisations is that they make space to accommodate aspects of Thai street life, such as food vendors. [Our street life] is a magnet, especially for tourists. It brings people to their destinations and gets them coming back.”

With this in mind, and with support from the Bangkok Metropolitan Administration, the Urban Design & Development Center is currently restoring or reviving 15 historic sites across town – including a flagship site at Tha Din Daeng on the Chao Phraya riverside – in the lead-up to the city’s 250th anniversary.

For the Tha Din Daeng project, the Urban Design & Development Center organised town hall-style discussions, connecting community leaders with activists, academics and property developers. According to Punnoi, although common in the West, this sort of all-inclusive communication is rare in Bangkok. Its application is timely, however. By rallying support from all parties for places that might fall victim to gentrification, they’ve managed to save iconic food spots like Thanusingha Bakery, a small shop where a very local sweet called khanom farang kudee jeen (an egg-based cake influenced by Portuguese and Chinese settlers) has been made for more than a century.

“What we are doing now may not exactly be a picture of the future, but it’s a good starting point,” Punnoi said. “We’re trying to [piece together] the right activity in the right place at the right time – it’s an exciting time to be involved with this.”