There are no striptease clubs in Seoul due to the legalities. Most places don’t advertise online. You might stumble upon something while exploring Seoul but best have a local guide. Watch out for the police running occasional raids. They’re just for show but they can be scary, especially for foreigners.
Luckily there are alternatives and there is a unique side to the erotic club scene in Seoul. They’re called “bangs”, in short, they’re just “rooms”. Something between a karaoke and a hostess club, most often reserved for Korean businessmen and their colleagues. The chance of getting in for a lone foreigner is close to zero. You rent a room and you choose a girl or a few from the available stable. It’s more of a social thing, but there’s always a slim chance for a bit of touching or a hand job. 30 minutes will cost you around $40.
Some other establishments, also sometimes referred to as “full salons”, will have rooms upstairs and allow you to have sex with the hostess. There are also “talking whiskey bars”, where you pay a girl $50 to sit around and get wasted with you. And especially in the thriving Gangnam area, the number 1 party district of Seoul, you will come across so called “blowjob bars” and “daedal rooms”. There basically everything goes, apart from full sex.