He denied it in 1993, and again in 2005.
When asked directly, he answered with a flat "no", and even asserted in one interview, "I'm not a homo. I'm not gay."
At the launch of his coffee-table book Kumar: From Rags To Drags on Tuesday, however, the veteran stand-up comic seems to have decided to come out at last.
Explaining why he waited until now to do so, the 43-year-old said, "When you're 40-something, people take you seriously. And when you tell people you're 40, anything you say, they will believe."
In his early days, he told The New Paper, he denied queries about his sexual orientation because he did not know how to handle them.
And even though his homosexuality is pretty apparent to most people, Kumar said emerging from the closet wasn't a walk in the park.
"If I want people to understand me, I think I have to be able to open myself," he said. "How to help people when I myself am in denial?"
The coffee-table book, he said, promises to reveal a side of him that the public has never seen. One chapter, entitled "Fairy Queen", is the most telling of his newfound openness.
In it, he also shares stories about his difficult childhood, relating that he was molested by an older man at the age of 10 — the experience that made him realise his preference for men.
Kumar also opens up about his current relationship with an unidentified 23-year-old man.
He says that his partner goes out with girls, even though he isn't okay with it, although he accepts it, saying, "If he is cheating on me, he'd go out with another guy."
He ends the chapter that details his relationship with his partner by saying, "There may not be a happily ever after, but we are in this relationship happily."
In other parts of the book, Kumar spoke of public perceptions and expectations of him as a performer.
"When people see me on TV, they think that I'm their friend and expect me to say more," he said.
"If you want a picture, I'll do it. But after the picture, if you want a conversation, I can't. I don't know you," he added, expressing his need to be able to separate his real friends from acquaintances.
He also dispels rumours of being promiscuous, saying that people assume he sleeps with the many male friends he has around him.
With regard to people saying that he only dates Caucasian men, he says, "Caucasian men don't even turn me on."
Supportive guests at Kumar's book launch include Minister for the Environment and Water Resources Vivian Balakrishnan, who said that Kumar looked like a "child bride", and is still going strong after more than 20 years in the entertainment industry.
"The way he dresses, the way he talks, the style of his jokes. These are the things that will always stay in my mind," the minister said on Tuesday.
Former foreign minister George Yeo is also quoted in Kumar's coffee-table book, speaking of a time he was interviewed by Kumar about a project where four sections of the Berlin Wall were displayed at Bedok Reservoir.
"It turned out to be one of the best interviews I've ever had. Kumar is a treasure," he said.
She said at the launch, "Kumar has established himself as who he is. It doesn't matter what he is… there is only one Kumar and he can get away with things that other people can't… he can be whoever he wants to be."
Celebrity host and comedienne Patricia Mok also said of him, "Kumar is daring in his stage work but most important (sic), he is a beautiful person."