For all that he's keeping it loose and easy, Dick's putting together the pieces from what he's seen of the 'high king' so far. The cut off titles indicates that he's not a huge fan of formality, despite being 'high' king. As does the fact that he gave his name without the title first. The lack of drawn weapons at any point says that not only was his story believable but it doesn't indicate anything sinister, at least not to anyone here. And the wry smile is a good sign; kings with a sense of humor are much easier to deal with than those without.

He considers lying for half a second to see what the result might be; it's best to test kings out in the wild where there aren't guards to stab you if you get it wrong. But his general gut feeling about the guy is good. So the answer pops out, almost immediately.

"I know how to ride."

Between being Robin and growing up on the Wayne Estate, it would have been stranger if he hadn't known.

"And how to hold on to keep from falling off the back of the horse."