The Brief: Kek or top kek can be a way to say "LOL," and a reference to a semi-ironic far Right ideology.
Kek comes from the Korean version of LOL. It is also associated with an ancient Egyptian god representing primordial darkness. The phrase is used by members of the Alt-Right, often on 4chan to refer to a satirical faith based on the idea that Pepe is the modern reincarnation of kek. The kek ideology is absurd – and the concept is used largely as an inside joke to troll liberals.
Top kek means that something is very funny, very good, the funniest, or the best.