“We are worried about a possible spread among the Thai community during their gatherings, so we have liaised with the Thai consulate hoping they can help distribute bottles [for virus tests] to its nationals,” said Dr Chuang Shuk-kwan, head of the communicable disease branch of the Centre for Health Protection (CHP).

Chuang said the Royal Thai Consulate-General told them it would distribute sample bottles to the estimated 100 Thai nationals who visit there each day.

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Of the four Thai cases, two have been stranded in the city since March due to Thai restrictions on flights to the country.

One of the patients among the group, a 38-year-old, was confirmed to be infected on Monday. Chuang said she had stayed with five other Thai friends at the Holly Mansion in Tsim Sha Tsui, then later at the Stanford Hillview Hotel in the same area.

Four of her friends had been quarantined, while one, a 35-year-old woman, tested preliminary positive on Monday. Health authorities are still tracking down the fifth friend.

That 35-year-old friend had hung out with a 27-year-old Thai housewife, confirmed to be infected on Sunday.

Chuang said the housewife had provided false information to authorities earlier, and that the administration would consider prosecuting her. The housewife allegedly told the Centre for Health Protection that the 35-year-old friend had already returned home, when she was in fact still in the city.

“There are still some untraced cases in Hong Kong, showing there are invisible carriers,” Chuang said.

Chuang also shed more light on the possible outbreak at Tsim Sha Tsui’s China Secret bar, where a local student and a Thai woman later found to be infected visited on September 23.

She said there were about 20 customers that night, and authorities were still tracking down one or two of them. The rest had already been quarantined.

Bars in Hong Kong have only recently been allowed to reopen after being closed amid the city’s third wave of Covid-19. But a maximum of two customers are allowed at each table, compared with four for restaurants.

The health authorities have requested police help in tracking down people who had recently visited the bar.

A source with knowledge of the investigation said the Thai woman who visited China Secret on September 23 first entered the city on March 16 – nine days before the Hong Kong government imposed a ban on foreign arrivals.

The woman had permission to stay until September 30, a day before she was confirmed as infected, and had been hospitalised since, the source said.

The woman told police she did not work as a bar girl, as some local media reports have suggested, saying she only went to China Secret to hang out, according to the source.

The bar is located on the third floor of the Lee Chau Commercial Building. The Liquor Licensing Board’s online registry has no record of it holding a license, though Club Bro – registered at the same address – does have a permit.

On Monday night, the Food and Environmental Hygiene Department confirmed Club Bro had a liquor license, while China Secret held a restaurant licence allowing it to serve light refreshment.

Health officials ask police to help track down bar patrons as fears emerge of new cluster

Professor David Hui Shu-cheong, a respiratory expert from Chinese University, said there was no evidence to suggest a major outbreak was looming among the Thai community, as there had only been a few recent cases.

“And they did not all stay in the same hostel,” said Hui, an adviser to the government on its pandemic response. “It’s hard to monitor, because they’re travellers. Reducing the length of stay permitted when granting a travel visa could be a way to control the situation.”

At present, travellers from Thailand can visit Hong Kong without a visa for a period not exceeding 30 days, though they may apply to the Immigration Department to extend their stay.

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Thai nationals returning home must first present a certifying letter issued by Thailand’s diplomatic offices or its foreign ministry.

A Thai national teaching the language in Hong Kong said there was a long queue of people waiting to do just that, and that it often took one or two months to get approval. As a result, the teacher said, some could find themselves stuck for some time.

Thailand’s consulate did not respond to a request for comment on Monday evening.

Separately, among the 11 new infections recorded on Monday, just one local case was untraced. The patient was a 46-year-old woman, a clerk, who had dined at a buffet at Gateway Hotel in Tsim Sha Tsui, but wore a mask while getting food.

She lives in Rambler Crest in Tsing Yi.

Additional reporting by Victor Ting and Christy Leung