By Manesha Pereira and Masayuki Kitano

SINGAPORE (Reuters) - After serving only a handful of customers in five hours on a recent weekday, Sam Goh said he was worried the sportswear shop he manages, LIV ACTIV, will eventually join other brands in leaving Singapore's Orchard Road shopping boulevard.

Singapore's reputation as a shoppers' paradise, which saw investors pour S$10 billion ($7.25 billion) into retail developments here in the past five years, is taking a pummeling because of weakness in the local economy and a drop in spending by tourists. Commercial space has increased by a tenth in that period, but vacancy rates have risen to 7.3 percent from 5.0 percent and industry analysts expect them to keep rising.

"Instantly when you enter this mall you see emptiness," said the 44-year-old Goh, whose shop gave up a quarter of its space last month to cut costs.

Further down the street, cashiers play games on their phones, while some shop assistants have improvised a mini-golf game along a quiet corridor of a shopping center. Thirteen of 16 units on the 5th floor lack tenants.

Store space in places with lower foot traffic is getting few takers. For example, in a suburban area on the west side of Singapore, more than two-thirds of a basement shopping center that has been open for almost two years remains empty.

These are all signs of bets that have gone wrong: that the domestic economy would remain robust, allowing demand from this city state of 5.5 million people to stay strong, and that retail splurges by visitors from the rising middle classes in China, India and Southeast Asia would keep increasing.

For Singapore this is not a small thing - wholesale and retail trade vies with manufacturing to be the biggest contributor to the city-state's gross domestic product and it is the biggest employer here.

But the sluggish global economy has put a brake on spending by Singaporeans, especially workers in hard-hit export sectors. Shoppers from abroad, meanwhile, spent 7 percent less in the first nine months of 2015 than they did in the same period of 2014.

LANDLORDS HIT

Wealthy Chinese, hit by an economic slowdown and a corruption crackdown at home, have less appetite for the luxury items they flocked to Singapore to buy during the boom years.

China also has built many of its own luxury malls and has even set up duty-free paradises in local tourist hot spots to lift consumption and spur domestic tourism.

And Indonesians, Thais and Malaysians now have cheaper versions of the same products back home. A luxury bag made by Coach <COH.N> can now cost twice as much in Singapore as in these countries.

In Bangkok and Jakarta, retail space has risen 20-25 percent in five years, with vacant space shrinking, data from real estate firm CBRE shows.

"Many rich Chinese used to come and spend money on luxury items and that is no longer the case and in the region you have a lot of competition," said Christine Li, director of research at commercial real estate services company Cushman & Wakefield.

"I am pessimistic about retail here," she said in reference to Singapore.

The deteriorating retail outlook is among several challenges faced by Singapore's property sector, which includes developers and real estate investment trusts or landlords, with shares of companies such as Frasers Centrepoint <FRCT.SI>, Capitaland <CATL.SI> and Wheelock Properties <WPSL.SI> losing 10-20 percent in the past 12 months.

More than 2 million square feet of new retail space will be ready for occupation in Singapore by the end of 2017, and it won't be easy to find tenants. But many of the bigger developers are partially protected from the downturn because they are present across segments like hospitality or homes in other Asian markets and beyond.

"Over the next three years you can see that supply is fairly strong and although the first quarter was fairly resilient, you’re not seeing much revenue growth," said Joshua Tan, an analyst with Maybank Kim Eng, referring to real estate investment trusts. He said that many of the retailers suffered from having similar product offerings to their rivals.

Sales of apparel and footwear in Singapore dropped 3.5 percent year-on-year in March and 14.6 percent in February, with brands such as British apparel brand New Look and Celio of France planning to close branches in Singapore this year.

Seth Kok from SG Debt Busters, has seen a 23 percent increase so far this year in shopowner clients seeking advice on how to reduce debt or deal with bankruptcy.

Retailers "expanded way too fast," said Kok. "But things turned bad ... everything started when China slowed down."

THE GREAT DISCOUNT

Internal factors are at play as well. Measures to give Singaporeans priority for jobs have curbed the number of expatriates on juicy salaries. Wage growth is expected to slow to 2.5-3.0 percent in 2016, compared with a 10-year average of 3.6 percent.

"We cannot fight these major trends," said Stephen Goh, executive director at Orchard Road Business Association, mentioning the job curbs, a strong currency, weaker tourism spending and a tendency for more Singaporeans to shop in cheaper malls overseas.

Many hopes are pinned on "The Great Singapore Sale", an annual marketing event, which started on Friday and will last 10 weeks this year. But discount signs have been ubiquitous across the island for some time.

Robinsons department stores have been offering up to 70 percent off a variety of goods for the past two weeks.

Rising interest rates prompted by the U.S. Federal Reserve's hike in rates in December have also restrained domestic spending. Mortgage consultants say the monthly cost of repayments on a mid-range condominium apartment goes up by S$400 for every 1 percentage point rise in Sibor.

"My family and I used to shop ... almost every week," said 50-year-old store manager Dino Ahmari, who pays a mortgage. "Now we make it a point to spend only once every two months."

($1 = 1.3794 Singapore dollars)

(Additional reporting by Fathin Ungku, Jongwoo Cheon, Aradhana Aravindan and Marius Zaharia; Writing by Marius Zaharia; Editing by Martin Howell)