Start by separating express buses from intercity buses. They overlap in the kinds of cities they serve, but they are not one booking system, and the exact departure and arrival terminal matters.
For international visitors, the most useful current guidance comes from Korea Tourism Organization’s 2026 transportation sheet. It says foreign-issued credit cards are accepted at express- and intercity-bus ticket machines and counters. For online booking, it lists Klook and Hanpass for express buses and Hanpass for intercity buses, with foreign-issued cards accepted through those visitor-facing channels. The same guide says foreign-issued cards are not accepted as direct tap payment on ordinary bus card readers, so local bus rides should be treated separately from long-distance coach tickets.
A practical workflow is: identify the exact departure and arrival terminals first; check the route and date; use a visitor-facing online channel where available or buy at the terminal; keep the booking or ticket confirmation; and arrive with enough time to find the correct platform. On busy weekends and public holidays, seat availability can tighten quickly.
Do not assume every direct operator website, app, card issuer, refund flow or ticket-collection method works the same way. These conditions can change by platform and route. Before travel, recheck the exact departure, seat availability and the current payment and ticket-collection rules for the channel you plan to use.