Marathoner Soh Rui Yong's run-in with the Singapore National Olympic Council (SNOC) over the SEA Games personal sponsorship blackout period has brought into sharp focus the issue of ambush marketing.

The term is used to refer to attempts made by brands which are not official sponsors to associate themselves with an international event.

Soh had earned the ire of the SNOC in recent weeks by promoting his personal apparel sponsor and drink sponsor - which are not the same as Team Singapore's backers - on his social media accounts.

This was in breach of the agreement he had signed as a Team Singapore athlete prior to the SEA Games. The agreement includes the blackout rule - which is in effect from Aug 5 to Sept 5 - on promoting personal sponsors.

At the heart of the matter is money, without which professional sport would not exist.

Major international sports events like the Olympics or the SEA Games draw a lot of attention (the Rio Games had a television viewership of 3.6 billion), but also require no small sum of money to stage, which is where sponsors come in so that taxpayers do not have to foot the bulk of the bill.

These sponsors are, by and large, protected under Rule 40 in the Olympic Charter, which requires athletes not to allow their image to be used for advertising purposes during a limited period either side of a Games. This is meant to prevent the value of sponsorship from being diluted by the appearance of rival brands or personal sponsors.

In the same category as Games sponsors are the sponsors of national sports committees like the SNOC, which pay to be affiliated with a country's athletes at major competitions.

This is where Soh, in highlighting brands that are competitors of Team Singapore's supporters, fell foul of the SNOC rules.

"(Soh's) personal sponsors would have benefited commercially from the exposure as this period is when most people would associate the athlete with the SEA Games," said Rajah & Tann lawyer Lau Kok Keng, who specialises in sports, gaming and entertainment law.

Soh is hardly the first athlete to test the boundaries of Rule 40.

A study by the Nielsen Company found that Nike's 2010 "Write the Future" campaign, featuring football stars Wayne Rooney and Cristiano Ronaldo, scored the company twice as many references in online English-language messages related to the World Cup that year than its competitor and official World Cup sponsor adidas.

However, Lau warned that while an individual athlete and his sponsor might benefit personally, there could be a heavy price to pay if an upset sponsor walks away.

"Things could come to a point where a brand like (SNOC apparel sponsor) Yonex starts asking why they are putting all this money into a team or an event that cannot protect their rights," he said.

"And if sponsors don't come forward, funding is reduced across the board and everyone is worse off."

Individual athletes too need money, however. For many Singaporean athletes, the job of full-time training does not come with a regular pay cheque.

"The blackout does make it very hard for many athletes to attract sponsors and present value to them when they cannot offer branding and publicity during what is often their biggest competition in a two-year cycle," said Deloitte Singapore and South-east Asia sport business group leader James Walton.

"But the counter-argument is that the blackout periods preserve the value of SNOC's sponsorships, which in theory fund the training of and benefit every athlete, not just the high-profile few that can attract personal sponsors."

Both Walton and Lau pointed out that there is a certain degree of leeway given to personal sponsors during international events anyway.

"At the end of the day, there are so many kinds of grey areas. Rui Yong's Asics shoes will be seen during the race. And by now, everyone in Singapore knows what brand of shoes he wears," said Walton.

Added Lau: "Most companies involved in the sporting world sponsor events themselves so they cannot have double standards. Their logos will still be seen in competition, so does the blackout for personal promotions really have that much of an impact for non-sponsors?"

Greater clarity from SNOC to athletes about the Team Singapore membership agreement could also help prevent similar disputes from arising in the future, he added.

"Many athletes I've encountered are often not aware of the full contents of the agreements they sign. Footballers, for example - they just want to get paid and go out and play," he said.

Change has been in the air for Rule 40 since before the Rio Olympics, when the International Olympic Committee relaxed its rules to allow athletes to promote long-standing non-official sponsors during the Games period as long as they do not use any Olympic properties or references, subject to approval by the athlete's national sports committee.

Still, whether or not exceptions will be granted to athletes like Soh is a question best tackled after the Games, felt former national shuttler Derek Wong, who urged sportsmen to stay focused on their immediate tasks: "The only thing you should be looking forward to now is your performance."

And that is exactly what Soh has done by retaining his gold medal.