I suspect it is a different (and incorrect) spelling of "λέμε", "we say", that is used for emphasis, in casual speech or slang. You'd say, for example:
-Καλά, η ταινία ήταν γαμάτη, λέμε!
I have no idea why the different spelling, though. It must be some slang variation, maybe someone else could help us out.
It's «λέμε» (we say), first-person plural of the verb «λέω» misspelled at first and then spread as a greek meme. And not a particularly clever one imho...
It's simple. Sometimes, «λέμε» (we say) is used as an intensifier at the end of a statement, e.g. Τρελά λεφτά, λέμε!, similarly to the British "I'll say (so)".
Λαίμαι is an ungrammatical, unorthodox variation used mockingly, frequently signifying that the person writing it thus is in a playful mood or is "slanging it", as it were.
Edit: I say! Πάλι καταϊδρωμένος! Εδώ χιονίζει πάντως. :)