He pretended to be a professor in child psychology and lied to the authorities about his HIV status to land jobs at two local polytechnics.
He even used his boyfriend's blood for an HIV test so that it would test negative for the condition.
Over a period of about eight years, American citizen Mikhy K. Farrera-Brochez, 32, committed multiple offences, including cheating, lying to a public servant, possessing drugs and using forged educational certificates.
Yesterday, he was sentenced to 28 months in jail. He pleaded guilty to a total of six charges, with 17 taken into consideration. Three other charges, which had been taken into consideration, were stood down to be mentioned at a later date.
In 2008, Farrera-Brochez moved to Singapore a year after he got into a romantic relationship with local general practitioner Ler Teck Siang, 35. The pair had met online.
To apply for an Employment Pass (EP) to stay here with his boyfriend, he submitted an HIV-negative test result to the Ministry of Manpower (MOM) in March that year.
But Farrera-Brochez, who is in fact HIV-positive, had used Dr Ler's blood for the test. He had visited a clinic in Commonwealth, where Dr Ler, who was a locum GP, was on duty. Dr Ler had drawn the blood from his left arm earlier that day and labelled the test tube with Farrera-Brochez's particulars.
MOM then issued Farrera-Brochez with an EP, and he later worked as a polytechnic lecturer.
Dr Ler, an infectious diseases specialist, worked as a medical officer at the Communicable Diseases Division of the Health Ministry from February 2012 to January 2014.
Farrera-Brochez similarly duped the authorities again in 2013, when he tried to apply for a Personalised Employment Pass.
He was also found guilty of possessing a ketamine and cannabis mixture in May last year.
Investigations further revealed that his various educational certificates, including one from the University of Paris, were forged.
Deputy Public Prosecutor Suhas Malhotra said that Farrera-Brochez knew that foreigners with HIV are not allowed to work here, and yet he had conspired with Dr Ler to falsify the blood test results.
"The fact that the blood test was supposedly performed by a doctor and issued by a clinic gave it an aura of authority, making it virtually certain that MOM would be deceived," he said. "His conduct evinces a blatant disregard for the authority of our laws."
Dr Ler, who has been charged in relation to the case, has yet to be dealt with.