A hawker's assistant and a Chinese national who entered into a sham marriage, for which the former was paid $3,000, were each jailed for six months after being convicted in the district court.

Cheng Yew Kwang, 48 and now unemployed, and Chen Yanjie, 40, an accounts analyst, were also given an additional six weeks each over several charges in relation to the Immigration Act. Both are appealing the conviction and sentence.

District Judge Salina Ishak, in judgment grounds released last week, wrote: " In my view, sham marriages are difficult to detect as it would not be feasible for the authority to go behind every marriage certificate to ascertain whether a couple is in a true marital relationship."

She added that the same applied to Visit Pass applications, given the high volume of foreigners who enter Singapore for various purposes.

The judge said it was "fortuitous" that Immigration and Checkpoints Authority (ICA) officers detected the sham marriage through vigilance, pointing out the extreme difficulty "when the parties take steps to conceal the offence as well as portray a picture of genuine marital bliss".

A dozen such sham marriage cases had been dealt with by the State Courts in the 11 months till June, involving Vietnamese, Chinese and Indian spouses, she noted.

Cheng had admitted in a statement that he was paid $3,000 by one " Ah Bak " to enter into the marriage of convenience with Chen solemnised in December 2012 in a Joo Chiat Road restaurant. No family member was there. As her spouse, Cheng served as her sponsor when she applied and was allowed to enter Singapore on a Visit Pass thrice in 2013.

She wrote Cheng's Ang Mo Kio address as her residence on the application. When probed, Cheng admitted that she did not live there. He was told by " Ah Bak" to put her clothes in his bedroom and to give her a set of house keys. Cheng was also advised to take her to his flat and familiarise her with the area.

The judge found that the case involved deception of the Registry of Marriages and ICA by the couple. The couple had used the fake marriage to allow her to remain in Singapore. Chen had also supplied a false address to enter Singapore.

The judge rejected Chen's claims that she had known the groom since 2012, expressing disbelief at photos produced as proof of an alleged wedding dinner. Noting a Singapore flag in the background, she said it was unlikely that coffee shops would display the flag in January.