KEVIN CLASH, the man, and the voice, behind "Sesame Street's" Elmo, resigned yesterday, as yet another man came forward and claimed he had a sexual relationship with Kevin when he was underage.  A 24-year-old man named Cecil Singleton is suing Clash for $5 million, claiming the two of them engaged in, "sexual activity" when Singleton was 15, roughly nine years ago.

In his lawsuit he said that he, "did not become aware that he had suffered adverse psychological and emotional effects from Kevin Clash’s sexual acts and conduct until 2012."

The lawsuit calls Clash, "an unmarried adult male living a prominent public life centered around the entertainment of toddlers, while at the same time he was, in secret, preying on teenage boys to satisfy his depraved sexual interests."

And it accuses him of, "trolling gay telephone chat line rooms to meet and have sex with underage boys."  That's how Clash met Singleton, whom he "groomed" by giving him money and taking him out for expensive dinners.  (You can read the lawsuit here.)

It's probably important to note that Singleton says he and Clash didn't have actual INTERCOURSE until AFTER he was an adult.   All that occurred over a period of two weeks when Singleton was 15, but then he ended the relationship.  The two of them hooked up again several years later when he was of legal age.

But Singleton said he believes that if they'd stayed together when he was 15, he believes they WOULD HAVE had sex at that time.  (Here's video.)