Sherine Toh says her best days at work are when none of the 600 or so staffers at Singapore's Tung Lok Restaurants quits, though such days are rare.

The Chinese restaurant group is one of the thousands of businesses struggling with a labor crunch caused by curbs on foreign workers that threaten the city-state's already feeble growth rates.

"It has gotten much tougher compared to the old days, five years back," said Toh, who has at least 20 vacancies to fill at any one time as head of human resources. The group closed some outlets because of the shortage.