At around 3pm on Tuesday, the men entered the Geylang Serai Bazaar, taking photographs and videos like the many visitors soaking in the festivities.
Minutes later, they scattered to a few stalls, identifying themselves and demanding to see the identity cards and work permits of some workers, a few of whom leapt on tables and ran to escape arrest.
"When I first heard the commotion, I thought some people were fighting," recounted eyewitness Ahmet Akpinar, 37, who sells Turkish ice cream at the bazaar.
The joint raid by the Ministry of Manpower, National Environment Agency and Singapore Police Force nabbed 22 unlicensed workers.
And going ahead, there should be more of such spot checks, said Pasir Ris-Punggol GRC MP Zainal Sapari, who is also assistant secretary-general of NTUC.
He told The Straits Times that he believes some of the workers are from neighbouring countries and are here on social-visit passes. "I don't think they work in Singapore," he said.
Stallholders at the bazaar said that some of the workers who were not nabbed on Tuesday have since returned to work.
Said Mr Zainal: "I think in order to make sure that the message is clearly communicated, it cannot be a one-off joint operation."
The issue has been brewing, he added, and for the past one to two years, Marine Parade GRC MP Fatimah Lateef had been "pushing" the authorities to conduct checks. She could not be reached last night.
While it is unclear just how prevalent the problem of hiring illegal workers is, indications are that it may be quite rife at the bazaar.
Two stallholders estimate that there are more than 50 such workers there. Mr Imran Marican, 26, who sells traditional drinks, said: "You can tell when you look at someone that they are a foreign worker. Especially when you speak to them, they have accents and usually they speak broken English."
A WhatsApp chat group for some of the stallholders broadcasts warnings of raids from the contractors who lease out the stalls.
"Most of us are in that group, so we are all aware," said Mr Imran. Added Mr Akpinar: "Once someone hears that someone is doing checks, they will inform the rest."
The bazaar organiser, Geylang Serai Citizens Consultative Committee, as well as contractors in charge of the various tents, did not respond to queries.
When asked what would prompt stallholders to hire illegal workers, many cited manpower issues.
Mr Edward Koh, 28, owner of The Raclette Factory, which has a stall there, said: " It's really difficult to get local people to work in a pasar malam."
Mr Andrew Selvarajoo, 28, who sells prawn vadai, said: " People employ illegal workers because they can pay them less than a local worker. Locals typically get between $7 and $8 an hour, while foreign workers can get only $40 a day."
The bazaar will run till June 24.