in Polish slang, what is the difference between Siema and Siemka?

Siema is a slang contraction of "jak się masz?"

"siema" - was invented by Jurek Owsiak :)

too much"analysis paralysis" in replies! siema means "howdy" hi, how ya doing ,hello, etc

It's a similar thing in all Slavic languages apparently, diminutive means little, if a word ends with a consonant in Russian, for example, the diminutive would be an "ik" or "chik" ending; knife: nozh, little knife: nozhik. If it ends with a vowel, to make it diminutive, you would typically put a "k" before that vowel and something before that if it doesn't really work, possibly change the vowel too, but basically thesame rule; field: polye, little field: polyushka