I recently became aware that my girlfriend, who has a Chinese passport but a B2 U.S. visa, can get 30 days in Seoul visa exempt provided that she has a "confirmed flight ticket from South Korea to the United States within 30 days of arrival."
Can we book a refundable ticket to the U.S. to get in and then fly to a different third country instead (rather than the visa issuing country)?
You could try it, but the risk is not negligible. There are Immigration exit checks in Korea, and they are thorough – and the boarding pass is required and scanned. And they keep all records, including the departing flight. Should the officer notice that a Chinese citizen was in Korea on a visa exemption, and gamed the system, there will be consequences. Keep also in mind that Koreans are not very big fans of Chinese people, and vice-versa.
Korea keeps all records about visitors, so should your girlfriend pass through unscathed, there's no telling what kind of reconciliation is done later, and what would happen should she try to come again to Korea. Like, for instance, on the way back...
The airline that checks you in at Incheon will also check the visa status of the passenger, and notice there's no visa. They will then ask for a reason. Visa exemption eh? And will probably deny her boarding, and notify Immigration (which, let's not forget, is a branch of the POLICE. Where's the emoticon for handcuffs?).
Generally speaking, airlines in Korea are extremely careful with who they transport. They check your legal status both in Korea and the destination country.
Bottom line, it'd be much safer not to try it...
