Two aspects to this. One would be legal
I'm not knowledgeable about S. Korea's legal environment. Though, I'd be surprised if something like this wouldn't at least violate the Hotel's acceptable user policy.
The other aspect would be technical
From a technical perspective, I'd make sure that I was using a different channel than the Hotel's APs.
If it was convenient, I'd probably want to use a MAC changer utility on the router...
I would also keep the router turned off when I wasn't using it.
Realize that if they want to, its not too hard to
track down a rogue access point.
Best of luck,
Uno