Can I sell my SaaS / app to Korean customers without setting up a Korean company?

Short answer: yes, for a while. I've watched a few foreign tools do exactly this — run on an international payment processor, invoice in USD, no Korean entity. It works until it doesn't. The friction shows up in three places. First, B2B sales stall the moment a Korean company's finance team asks for a tax invoice — they need one to expense your product, and you can't issue a proper one without a Korean business registration. Second, local payment methods: a large share of Korean consumers don't default to international credit cards the way you'd expect, and if you're not on the local pay options, you're invisible to a chunk of buyers. Third, app store payouts and tax treatment get messy. My honest take from the platform side: start without an entity to validate demand, but the day a real B2B pipeline appears, the tax-invoice issue alone will force your hand. Don't treat incorporation as step one — treat it as the thing you do once you have signal.