Suanbo is a hot spring town, so the thing to do is to go hot spring dipping. Most all hotels offer entry into their spa for W3000-5000, but it's worth it to make the 15-minute hike up to the Park Hotel on the western outskirts of town, which has the best views and the only outdoor tubs in town W6000, open 6 AM to 9 PM; separate facilities for men and women.
In winter, skiing at the nearby Blue Valley Resort 2 km away is a popular option.