He posed as a young girl on a social networking site and was shocked by the number of men who wanted to have sex with "her".
It did not matter that he claimed to be only 14 years old.
When they sent their pictures over, he put them on his Facebook page to expose them. There are pictures of nine men he claimed tried to have sex with the "girl".
Mr Fai Marwan, 32, a bachelor, works in the hospitality industry. He is on a mission to rid the Internet of "perverts and paedophiles".
Lawyers told The New Paper that while it is entrapment, Mr Fai is not breaking any laws. But neither are the men he exposed.
But he is determined to push on. He said: "For me, this is a form of community service and I will continue to do it."
He does not even hide his own identity on his Facebook page.
He told TNP: "I have nothing to hide because I am doing the right thing.
"I have my own reasons why I never went to the authorities with what I have uncovered.
"I am not doing this to shame people, I am doing this to create awareness so that parents and people are aware of what's going on online."
Mr Fai said it was a conversation with a friend two weeks ago which got him started. Till then, he was sure Singaporean men would not prey on girls under the age of 16.
After all, the law is clear - girls of that age are protected because of their lack of maturity.
And those who prey on them can be jailed for up to 10 years.
"But my friend said that's not the case," Mr Fai said.
"She said there are men out there who are eager to hook up with girls as young as 14 if given the opportunity, and many of them turned to the Internet for such kicks."
Mr Fai's friend, who wanted to be known only Ms Iyah, confirmed the conversation.
The medical equipment sales representative, who is in her 30s, told TNP: "We were watching a video on Youtube and the show focused on sexual predators targeting young girls in America.
"Fai was certain such things didn't happen here.
"But I challenged him to find these men because if he looked hard enough, he would find such men even in Singapore," she added.
Curious and determined to do the right thing, Mr Fai accepted Ms Iyah's challenge.
And the results were disturbing.