Clearly, Ren was so arrogant that he'd rather put his own physical health in danger than listen to him. Hux was sorely tempted to bring back his soldiers just so that he could tell the idiot to go to bed in front of them, but he dismissed the thought. It wasn't worth his time-- it wasn't worth of the time of his soldiers to deal with Kylo when he was being a stubborn fool.

"Very well. When you pass out, make sure you do it in a place where we can easily retrieve you later."

He almost sounded bored, almost uninterested in Ren's stubborn behavior. What was the point of getting mad over his blatant disrespect now? The Dark Jedi was just being so over the top that Hux didn't feel angry. Mild annoyance, yes. But not much more than that.