Hm, mono refers to a general category, doesn't it? Like, food and drink (tabemono and nomimono). You may consider the word koto こと - 事 instead, since it has the connotation of the singular.
saikou no koto shitteru ka?
さいこうのことしってるか?
Don't forget the question particle, ka か at the end
You may consider sticking a "you" pronoun like anata あなた or kimi きみ in there somewhere, too. What you use depends on the kind of feel your song's got. A more romantic, ballad-y song would be better off with kimi, as anata can be pretty distancing.