This is to differentiate interior design businesses from design-and build firms and renovation contractors.
There is an accreditation scheme in place for renovation firms, helmed by Case and the Singapore Renovation Contractors and Material Suppliers Association since 2014. It allows customers to claim from insurance companies for botched jobs.
Many design-and-build firms and renovation contractors often offer interior design services for free, Mr Ong says, though they factor the service into the final bill.
"The level of professional standards among interior designers here varies and untrained individuals can call themselves interior designers. The term is being abused," adds the 41-year-old, who is also the managing director of the award-winning, multi-disciplinary Nota Design Group.
He estimates that there are more than 3,000 interior designers and firms in Singapore.
Although the planning is in the early stages - a Sids accreditation scheme is likely to be ready only in a couple of years - some of the criteria are a designer's academic qualifications and his portfolio, he says.
Also under consideration is a fee guideline that helps interior designers know what price range is acceptable to charge for different types of projects.
Sids also wants to work with a government body to validate the accreditation scheme, Mr Ong adds.
The Interior Design Confederation Singapore (IDCS), a non-profit organisation and a registered society, is on the same page.
Since 2014, it has been working with the DesignSingapore Council, the national design agency, on an accreditation programme for interior designers.
Mr Alan Fan, 44, an IDCS executive council member and founder of award-winning architecture and interior design firm Topos Design Studio, says that accreditation for the industry is "long overdue".
He points to other countries that have regulation systems in place.
For example, the Philippines has introduced laws governing the interior design profession. Under the Philippine Interior Design Act of 2012, decorators, architects and furniture-makers cannot call themselves interior designers, and foreign designers have to get a permit and work with a local designer.
An accreditation scheme "will give the industry a new direction and improve its professionalism", Mr Fan adds.
Do interior designers want accreditation?
Some say yes; others question what criteria are relevant; while some feel it is simply impossible.
Established firms tend to be proaccreditation, especially in a saturated industry with low barriers to entry.
Mr Stanley Tham, 39, co-founder of 12-year-old KNQ Associates, says: "Some who claim to be designers may not even have a deep understanding of proportions, colour coordination or how to tailor homes to suit clients' lifestyles, instead, just following the clients' request to create something fashionable."
Even if there were an accreditation scheme, there could be disagreements on what criteria firms need to satisfy to get the badge.
One of the criteria Sids proposes is academic qualifications, but Design Intervention founder Nikki Hunt, 47, says: "A paper degree is certainly not a guarantee of competence."
"I have worked with several designers who have qualifications and been disappointed."
She points to successful designers, such as South Africa-born Kelly Hoppen, who do not have formal training.
Hunt moved to Singapore from Britain in 1993 and set up her interior design business a year later.
She says home owners should "look at the portfolio of the firm and for consistent quality".
Others feel that the industry - from interior designers to renovation companies - is simply too large and diverse to be regulated.
Mr Lin Weizhang, 39, principal at Super Fat Designs, a five-year-old multi-disciplinary interior firm, says that while accreditation is necessary, getting all interior designers on board would be "next to impossible".
He adds that as his firm relies on word-of-mouth publicity, being accredited will not snag Super Fat Designs more jobs.
While it remains to be seen how accreditation would work out for the industry, there are some informal safety nets for home owners.
Renovation and design platforms such as Houzz have options where home owners can leave reviews of good and bad services by interior designers listed on the sites.
Mr Jason Chuck, managing director of Houzz Asia-Pacific, says: "The Houzz team moderates all (reviews) for legitimacy and objectivity. We believe they serve as an independent voice that helps provide an informed view of working with that professional."
There is also Qanvast, a "one-stop shop" for home owners looking for interior designers and furnishings. It has a website and a mobile app, where projects by approved interior designers are displayed.
So confident is Qanvast of its stable of designers that last month, it launched The Qanvast Guarantee, which covers a home owner for up to 50 per cent of his contract value, or a maximum of $50,000 - whichever is lower. Home owners do not pay anything to be part of the programme.
The home owner has to request a quote and pick one of five interior designers recommended by the site. Once the home owner has settled on an interior designer, he can choose to send Qanvast his signed quotation within seven days to be covered.
Qanvast will make payouts to up to four home owners a year, or up to $100,000 in total.
Qanvast's operations and customer experience manager, Mr Johann Lim, says: "It's meant to give home owners peace of mind. We stand by the interior designers we endorse."
One of their customers is home owner Kenneth Tan, 28, a project manager with an IT publishing company who signed with 10-yearold Fineline Design, a Qanvast endorsed interior designer. His three-room Housing Board flat in Bukit Merah is now being renovated for $34,000.
Mr Tan says: "In the beginning, my aim was to find just someone who could renovate my house within my budget. The guarantee is an added value. I don't have to panic if anything bad happens because of the interior designer."
Correction note: In an earlier version of the story, it was stated that the Houzz team moderates all reviews for legitimacy and objectivity. Mr Jason Chuck, managing director of Houzz Asia-Pacific, has since clarified that Houzz reads every review submitted, in addition to having filters and flags in place to identify questionable reviews.