Soon after Sgt. Steven Lee was assigned to the 109th Precinct in Queens, he realized some of the cops there were oddly protective of “the karaokes.”

These gaudy nightclubs of neon and mirrors, clustered on, and just off, Northern and College Point boulevards, offered pay-by-the-hour private rooms where tipsy patrons, mostly Chinese and Korean, could shout along to a karaoke machine.

Drugs and women were also allegedly for sale, if you knew whom to ask.

“If you go out and try to summons somebody by one of the karaokes, you’ll hear from the lieutenant, or the detectives, or the other cops,” Lee says he noticed.

“They go, like, ‘Yo, leave that place alone. Do the right thing,’ ” he says. “Everybody in the 109 — and some from other commands — kind of knew about it. They knew what was going on.”

It was 2013, and Lee had just been transferred to Flushing after eight years at a precinct in Brooklyn’s East Flatbush.

Every precinct has cliques, and the 109 was no different. The Asian cops had a clique, led by Lt. Robert Sung, then 47, a wiry veteran with 20 years under his belt, who seemed to have a particular interest in the karaokes.

Sharing this interest was Sung’s right-hand man, Detective Yatyu Yam, then 34, a liaison to the Chinese community.

The two would stick their noses in anytime a 109 cop arrested someone in or around the karaoke clubs, or anytime vice or narcotics cops from outside the precinct made an arrest there.

“Sometimes we would do inspections, or we’d get a job, a 911 call to that area, and we’ll go to that location, and the cops would come up to you and say, ‘Hey, be careful. This is Sung’s place,’ ” Lee told The Post.

“And you’d be like, ‘What do you mean?’ And they’d say, ‘Sung hangs out here, so just be on your toes, or he’s going to f–k with you.’”

Lee quickly learned to look the other way and became a “conditions sergeant,” tasked with policing the karaokes and nightclubs. He answered directly to Sung.

“People had ideas that something shady was going on,” Lee says now. “But everybody turned a blind eye.”

“We have a saying — you put on your blinders,” he says.

In summer 2013, Lee says, Sung took him aside and confided in him something terrifying. There was a new commanding officer at the 109 — Thomas Conforti, a straight arrow who didn’t play along.

Sung wanted him out.

How about, the lieutenant suggested, we get one of the karaoke club hookers to frame Conforti for rape?

“We need to get rid of this guy,” Sung allegedly told him.

That’s the moment, Lee says, when the blinders fell from his eyes — when he decided to stand up for what is right, first as a wire-wearing, NYPD Internal Affairs anti-corruption informant, and later as a whistleblower against Internal Affairs itself.

Sung, Yam and the hookers of the karaokes were already in league, as Lee would find out while going undercover for Internal Affairs.

They’re known as “PRs,” for “public relations girls,” Lee explains of the pretty, flirty Asian women who greeted male customers in some of the seedier karaokes.

His life would never be the same.

Some of them had Yam’s cellphone number, and they’d call him if they wanted help with a customer off-site, Lee says.

“After they have sex for $300, she’ll change the price and be like, ‘Oh, you owe me $700. And the guy would be like, ‘No, $300.’ And she’d be like, ‘No, you’re going to give me $700 or I’m going to call the cops and say you raped me and robbed me.’ ”

It was the PR girls that Sung thought of first, when he plotted to get rid of Conforti, says Lee.

“I was like, ‘What are you thinking?’ ” Lee remembers asking his boss, as they drove to a pizzeria on 162nd Street off Northern Boulevard. “He’s like, ‘Oh, you know, have one of the girls from the karaokes claim that he raped her.’

“I’m like, ‘OK.’ I played along with it. But I’m not cool with that. That immediately struck me. That’s going way too far. That’s wrong.

“You see Conforti coming to the precinct with his wife, his kid, and he’s a stand-up guy. So even if there’s a false allegation like that, and even if he wins that false allegation, his wife and his family is always going to see him in that light. It’s always going to tarnish him.”

Lee told Conforti.

A week later, Conforti called Lee into his office. Would Lee be willing to work with Internal Affairs, get Sung on a digital recording trying to frame him for rape?

“All right,” Lee answered. “Fine. I’ll do it.”

Next followed several days of meeting in secret with his new Internal Affairs handlers, Lt. William Seeger and Sgt. Darrell Owens.

“They come to my house three, four times,” once with a higher-up, Lee remembers.

Lee learned to work various recording devices, signed some paperwork, and started hanging out with Sung drinking in the karaokes after work.

‘The NYPD told the feds, “We’ll take care of it, we could police ourselves.” That’s the biggest laughable joke out there. That’s like the fox saying he’ll watch the henhouse.’

Before long, Lee produced recordings filled with apparent corruption — and he continued to do so for the next year and a half.

He’d be introduced around the table. “They’re like, ‘This is so-and-so, he works with the chief,’ ” meaning then-Deputy Chief Diana Pizzuti, commander of Patrol Borough Queens North.

“This is so-and-so,” he’d be told. “He works vice, or narcotics. A lot are coming from outside the 109. There’s a lot of people, and it’s not just cops and sergeants and lieutenants — it’s higher-ups, too.”

They’d all drink free Tsingtaos and Hennessy. The “girls” were free, too.

Lee gave Internal Affairs all of this and more — describing a whole network of cop-protected karaokes, two of the biggest run by the notorious Jimmy Li.

“Jimmy, he’ll come in and go up to one of the girls and be like, ‘Hey, this is lieutenant so-and-so. You take good care of him.’ ”

Lee learned that Jimmy Li would pay Sung and Yam a regular stipend, thousands of dollars a month.

In return, Li would get a heads-up on upcoming drug or narcotics raids or DWI checkpoints. He would get favored treatment if his customers or workers were arrested.

“I’m like, listen,” Lee says he told Internal Affairs. “There’s a whole can of worms with this.”

Don’t worry, Lee says his handlers would tell him. Stick to the rape frame-up. Don’t get into anything else.

Once, in 2014, early on in the investigation, Lee made the “mistake” of arresting a roomful of people partying at the wrong bar — “one of Jimmy Li’s places.”

“I go into the room,” Lee remembers, “and there’s white powder on people’s faces. There’s a whole bunch of vials of white powdery substance. We thought it was ketamine or cocaine. A bunch of vials.

“We have three people in cuffs already, and I immediately get a phone call from Yam — while I’m at the scene. Yam is like, ‘Hey, what are you doing? That’s Sung’s place!’ ”

Let them go, Yam tells him. The next day, Lee got Yam on tape in the driveway of the 109, thanking him for letting the guys go.

“If you ever need anything, just let me know,” Lee claims Yam told him. “I’ll tell Jimmy. Jimmy will take care of you.”

Still, Internal Affairs was not interested. Don’t worry about it, he says they’d tell him. Stick to the rape frame-up.

“If I need anything from the karaoke owner, he’ll take care of me — isn’t that bribery or something?” Lee says now, still shocked by the lack of interest.

“I let three people go who had drugs — legitimate arrests! — and then they’re telling me they’re going to reward me for it if I want.

“So why don’t we go for this? And they’re like, ‘Just try to get the rape allegations.’ ”

Lee says he learned two seemingly contradictory things from his handlers as the investigation went on.

Then-Police Commissioner William Bratton was being looped in to what Lee was uncovering, his handlers boasted.

“This goes straight to the commissioner,” he says he was told, more than once, about who was being looped in about his undercover work.

And yet, his handlers had little interest in the wider corruption beyond Sung and Yam.

“The NYPD told the feds, ‘We’ll take care of it, we could police ourselves.’ That’s the biggest laughable joke out there. That’s like the fox saying he’ll watch the henhouse,” said Lee’s attorney, Eric Sanders.

Again and again, Lee said he would come back with good stuff — the protection racket that extended far beyond the precinct, the payoffs in free “girls.”

Twice, Jimmy Li told Lee that a lieutenant from Brooklyn had a partnership in a Third Avenue club that was filthy with drugs and prostitution. The lieutenant wanted to expand into the 109 Precinct, maybe set up a protection arrangement with Lee.

Never mind all that, Lee would again be told by his handlers. When Lee got good dirt on tape, he’d be told the recording couldn’t be uploaded, or it was inaudible, he said.

“Sometimes they’ll be like, ‘Oh, the recording didn’t work. It had no battery,’ or whatever.”

About a year passed, and Lee still hadn’t given Internal Affairs what they wanted — the Conforti “rape” frame-up on tape.

Internal Affairs hatched an alternate plan to get Sung and his sidekick, Yam, out of the NYPD.

Lee recorded Jimmy Li paying Lee $10,000 cash for framing a rival karaoke for drug charges.

Li was arrested and “flipped” against Sung and Yam, although ultimately, Lee believes that Li tipped at least Yam off to the Internal Affairs probe.

In December 2015, Sung and Yam were arrested. Years of widespread corruption, Lee insists, were reduced to a few bribery and misconduct charges.

Shortly after the arrest, at the NYPD holiday party, Jimmy Li was a guest and got a selfie of himself shaking hands with a seemingly oblivious Bratton.

Ultimately, Sung and Yam were able to plead guilty to lesser charges; both avoided jail and kept their pensions.

“Internal Affairs is supposed to police the police, but that’s not how it works. It’s all politics,” Lee says.

“Because, originally, in the case, I found out they were telling me the feds had something going in the 109. And then the commissioner actually talked to the feds and said, ‘Hey, let us handle it.’

“Because if the feds took care of it, they would have taken everybody down that were involved. And then it would have been a big thing, and the Police Department would have been embarrassed,” he says.

“They kept telling me,” he says of his handlers, Owens and Seeger, “that Bratton didn’t want to make it seem like there was all this corruption under his reign. So they kept it to just two people, to make it seem like it was just an isolated incident, and that it’s not a big corruption thing going on.

“But it is a big corruption thing going on.”

Owens declined to comment, his union said. Bratton did not return calls for comment.

“Internal Affairs fully and independently investigated these allegations, as we do in every case,” said NYPD Assistant Commissioner J. Peter Donald.

“Working closely with the Queens District Attorney’s Office, the case resulted in criminal charges against two police officers. Several others were also served with department charges.”

Sung pleaded guilty to attempted official misconduct and received a conditional discharge on Sept. 25, 2017.

Marvyn Kornberg, Sung’s lawyer, said his client has already faced justice. “He was charged with a laundry list. Nothing was able to be proven except that he accepted a meal from Li,” the lawyer said.

Yatyu Yam pleaded guilty to second-degree obstructing governmental administration and received a conditional discharge on July 6, 2017.

Lt. Louis Turco, president of the Lieutenants Benevolent Association, denied the allegations against Seeger, saying, “They [Lee’s IAB handlers] investigated every allegation that was brought to their attention. This sounds like somebody’s trying to get a payday out of this.”

Lee has now put the city on notice that he plans to sue for $35 million, alleging the NYPD buried the corruption in and around the 109th Precinct, then tried to bury his career to keep him quiet, giving him bad employee evaluations and desk assignments.

Jimmy Li, though, continues to thrive. “His places are even more wild now,” Lee says.

At 10:30 on a recent evening, a dozen young women in high heels and short skirts filed in a group into one of these clubs at 41st and College Point Avenue.

They made a beeline to the back, toward the club’s warren of karaoke rooms. At the bar, a bouncer complained about a recent close call with the cops.

“I’m just saying, don’t s–t where you eat, know what I mean, bro?” the bouncer griped.

The man then asked the bouncer, “What room did Jimmy get me?”

“One-oh-six, upstairs,” the bouncer said. The man and two other patrons stood up and headed upstairs.

Additional reporting by Alex Taylor and Laura Italiano