"People come here to play and to smoke," said Cheung. "It's always been the tradition to do both together."
For everyone involved here -- from the staff ferrying free drinks and cigarettes to the players themselves -- the marriage between the Chinese gambling game and smoking is one that shouldn't be broken.
Nevertheless, it is about to be.
Hong Kong's government is set to enforce a blanket smoking ban in public places from July 1, aimed at protecting workers in the city's bars, nightclubs, bathhouses, massage establishments and mahjong parlors from second-hand smoke.
Yet many workers regard the legislation as a death-knell amid a recession that has pushed the city's unemployment rate up to 5.3 percent. Bars have reported a drop in business as the slowdown bites.
"With the financial crisis, swine flu and now the smoking ban, it's a perfect storm of trouble for the entertainment sector in Hong Kong," said Lawrence Ho, who has run a bar here for 18 years.
"People are more worried about short-term job security than long-term health, because a ban is likely to make thousands unemployed."
The Entertainment Business Rights Concern group, a lobbying organization, says 95 percent of the nearly 100,000 owners and workers it represents fear they will lose their jobs if the ban is enforced.
The organization points to studies conducted in Britain that say bar and pub business declined by around 15 percent in the two years after smoking bans.
Suzanne Wu, from the Secretary, Catering and Hotels Industries Employees General Union, said workers were divided.
"It is very difficult to unify the opinion as different employees have different concern. But for long-term benefit, we (the union) support the implementation of the smoking ban," she told AFP.
For Cheung, business at his mahjong parlor is already down 30 percent from the previous year and he says a smoking ban will compound his losses.
"If you are playing mahjong with three strangers with money at stake, you can't ask them to wait five minutes while you go out for a smoke," he said.
Hong Kong banned smoking in public places such as schools, beaches, restaurants and karaoke bars in 2007, but the legislation was deferred for two-and-a-half years for certain establishments.
Now that the ban is about to be enforced, some are asking for more time and have even organized demonstrations.
"The current economic situation in Hong Kong is very bad and these people think they won't survive a smoking ban on top of it," said legislator Paul Tse, who supports a two-year deferment.
The government points to Census and Statistics Department figures that show restaurant business is up 30 percent since the ban was enforced two years ago.
"A number of establishments have attracted guests who are non-smokers or dislike second-hand smoke after the implementation of the ban," it said in a statement.
While cities such as New York and London have adapted to smoking bans, business owners here say Hong Kong?s high-rise living makes the issue more problematic.
Anita To owns two bars on the 20th floor of a building in the city?s nightlife district of Causeway Bay and says she fears customers won?t come back after they have dropped down to street level for a cigarette.
"A large percentage of my customers are smokers and I don?t think on July 1 they will quit smoking," she said. "Business is already down 50 percent and I think the ban will just kill me off."
Critics say the government?s watered-down introduction two years ago has caused the problems.
"It has brought confusion and challenges to the law, great expense and effort for the health and legal authorities, and bar workers continuing to be exposed to dangerous smoke," said Judith Mackay, a Hong Kong-based adviser for the World Lung Foundation.
And crucially it has delayed the tough new legislation until the fear of unemployment takes priority over the health of workers.
"Some of my staff have been breathing second-hand smoke for 30 years," said Cheung. "Right now they'd rather keep their jobs."