They have reminded staff to be polite to customers, and displayed their prices more prominently - in the aftermath of brawls at their eateries earlier this year.

These complement existing security measures at Balestier Bak Kut Teh (Kian Lian) and Heng Long Teochew Porridge, both of which have security cameras.

In the most recent case, two men aged 50 and 53 were arrested for allegedly causing a scene at the bak kut teh, or pork rib soup, eatery in the early hours of Aug 19.

Camera footage posted on the shop's Facebook page, with a description of the incident, showed cutlery being thrown and a bun steamer being pushed over.

It was an "unfortunate incident" that caused the shop "losses of at least $5,000 and damaged furniture", according to the post.

Speaking to The Sunday Times, the bak kut teh stall owner, Madam Wendy Tia, said: "Some netizens said it must have been the service staff's fault, and we have since reminded staff that no matter how busy they are, they should be more polite."

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She added that such incidents are worrying: "What if they threw glasses, and someone got injured?"

NOT UNUSUAL It could happen anywhere. It is normal because people could be triggered by an incident and fail to control their temper. SAFETY COORDINATOR BRENDON TAN, a regular patron at the coffee shop where Balestier Bak Kut Teh (Kian Lian) is.

The business has been operating since 1965, and its shop in Balestier is open 24 hours a day.

Staff at eateries that open late in the area said arguments and brawls happen occasionally, and are likelier to take place past midnight, when patrons arrive tipsy.

At popular eateries, staff may be too busy to spend more time attending to customers, they added.

It was the first time such an incident happened at the bak kut teh stall, said Madam Tia, who added: "Staff may have been busy that night, and left customers with the menu and cutlery without saying a word - this may have angered the customers."

When asked about possible reasons for brawls breaking out, she said: "Often, our late-night patrons are people who may be tipsy. It is hard to prevent such incidents."

But so far, other customers have not expressed concern, she said, adding that it helps that this case does not involve food quality. Business has not been affected either.

Safety coordinator Brendon Tan, 36, a regular patron at the coffee shop where the Balestier bak kut teh stall is, said he is not worried.

"It could happen anywhere. It is normal because people could be triggered by an incident and fail to control their temper," he said. "I'm used to it. I have seen fights elsewhere."

Mr C.L. Lee, 67, who works at 333 Bak Kut Teh, also along Balestier Road, said he has been working in the area for about 10 years and, in the past, has seen customers shoving each other or quarrelling. In such cases, staff often help to separate the customers and resolve the issue. "When there are too many customers and staff do not have enough time to attend to them, they could get impatient and angry, and disagreements could also spark from there," he said.

At Heng Long Teochew Porridge along Upper Serangoon Road, where fights erupted twice in three months, management took to displaying the prices of dishes more prominently on its menu.

In July, six people were arrested for brawling at the stall, and a 31-year-old man was taken to hospital. In May, four customers allegedly wrecked the place with wooden chairs, tussling with staff before tossing food on the ground and shattering a marble-topped table over a $28 bill.

A manager who declined to be named had told ST that he was used to such incidents. He said they happen once in a while, usually in the wee hours.

Staff at the store had told ST that improvements will be made - food prices will be more prominently displayed, for example.

Business owners in other areas where fights have occurred are also taking care to prevent any situation from escalating. For example, Fu Man Yuan, which occupies a unit in Yishun Street 22 at which a fight occurred while it was occupied by Yun Wei Restaurant and left four people injured in January last year -now has a security camera for its interior, in addition to one at its entrance.

Its owner Zhu Qin said: "Some customers said they are worried, but we tell them that the perpetrators back then have been arrested. Most customers are not out to cause trouble. If there are minor issues, we try to accommodate them."