Can I smoke in isolation hotels in Korea?

It depends on the hotel's specific regulations. If there is no regulation, you can smoke.

If the hotel clearly stipulates that smoking is not allowed indoors, then smoking is not allowed. It is best to comply with the regulations and requirements. If there is no explicit provision, please ask the hotel staff whether smoking is allowed. In most cases, smoking is not allowed in the hotel room, but only in the outdoor balcony.

You'd better ask the hotel service staff.