What started out as a favour to help his friends pass their Individual Physical Proficiency Test (IPPT) morphed into a scheme that cheated the Ministry of Defence (Mindef) of $24,700.

Salesman Lim Chun Chyi, now 37, who initially took the IPPT on his friends' behalf, also roped in friends to pretend to be other operationally ready national servicemen (NSmen) - sometimes for a fee.

Between 2011 and 2014, he and his friends took the IPPT for 72 NSmen and pocketed the Mindef incentive payouts.

Lim was caught on Dec 6, 2014, after an eagle-eyed fitness trainer at Khatib Camp noticed that he looked familiar. He recalled that the same man had taken the IPPT a few weeks ago.

Lim was jailed for 18 months yesterday after pleading guilty to 20 cheating charges involving $8,000. In each of these charges, he had attained the gold award for others. Another 73 charges for similar offences involving $16,700 were taken into consideration during sentencing.

According to court documents, Lim and two accomplices - Nicholas Tan Kun Sung, 37, and Kho Puay Meng, 39 - entered various army camps to take the IPPT on behalf of other NSmen. Lim was the only one who interacted with the clients.

Deputy Public Prosecutor Ng Jean Ting said Lim would either actively solicit clients or receive requests from them via phone calls or WhatsApp messages. He would then register for the IPPT on his clients' behalf.

DPP Ng said: "In return, depending on whether the accused obtained a gold, silver or pass-with-incentive award, the accused would receive the corresponding incentive payout disbursed by the Ministry of Defence to the NSmen as payment."

A gold award recipient is entitled to $400, while a silver award garners $200. A pass-with-incentive award is $100.

DPP Ng said the clients passed the money to Lim after receiving their payouts.

Occasionally, Lim would ask clients for an additional $50 fee for engaging his services. If they agreed to his terms, he would ask for their personal details and use these to register online via the NS portal for a time slot at one of the many army fitness centres islandwide.

He would then meet his clients to collect their identity documents, such as identity cards and driver's licences, to get into the centres.

He would go to the centres himself or get one of his accomplices to do so.

DPP Ng said Lim would give Tan and Kho a cut of the incentive payouts when they were involved.

The Singapore Armed Forces (SAF) Provost started its investigations soon after Lim was caught pretending to be someone else, and the matter was referred to the police in April 2015. On Sept 13 last year, Kho was jailed for two months after pleading guilty to one charge of conspiring to cheat. The case involving Tan is still pending.

Yesterday, DPP Ng told the court that Lim had made full restitution, and urged District Judge Low Wee Ping to jail him for between 18 and 24 months, stressing that his offences were difficult to detect.

Defence counsel Raphael Louis pleaded for nine months in jail, and said his client was embarrassed at bringing shame to his family.

When handing out the sentence, Judge Low said he agreed with the prosecution, adding that the fact the trio ran more than 80 times in the IPPT in three years as part of the scheme bewildered him.

Addressing Lim, he said: "You could have used your fitness for other positive outcomes but decided to take the criminal road."

Mindef said a total of 58 SAF, six Singapore Civil Defence Force and five Singapore Police Force NSmen had been disciplined according to the respective service's disciplinary framework.

Verification measures have since been stepped up to apprehend and punish those who attempt to cheat during IPPT. A Mindef spokesman said: "In addition to identity verification during IPPT registration, facial checks will also be conducted against their 11Bs or NRICs.

"Since the start of 2015, biometric fingerprinting technology has progressively been introduced at SAF camps to complement the existing security procedures."

A 11B is a military identity card.

Currently, Bedok Camp and Maju Camp are equipped with biometric fingerprinting technology.

To strengthen the security of SAF camps, all personnel, including NSmen taking their IPPT, will have to undergo biometric fingerprinting to get in by next year, said DPP Ng.

This applies to all SAF camps and fitness conditioning centres.

For each count of cheating, Lim could have been jailed for up to 10 years and fined.