Mueng Chob Kin comes from the Thai phrase written as มึงชอบกิน, a very informal way of saying you like to eat. The rude, familiar tone is part of why it works as a meme, it sounds like close friends teasing each other rather than polite speech. Online the clip circulates on Thai soundboards and in short form edits, usually captioned over eating scenes. It stays useful because the joke is universal, needing no setup beyond a person and food.