When learning Thai, I was amazed how modern Thai word "fish" is similar to Slavic word "to swim"
First, I looked into dictionaries of Slavic languages. Many, including Vasmer's Dictionary of Russian Language, refer Ancient Greek
πλεῖν, but no further references leading to PIE/Sanskrit.
Then I looked into Leiden Indo-European Etymological Dictionary and found that
but again, no reference to "fish".
So, my question is, how to prove that Thai "fish" and Slavic "to swim" are relatives?