1. Start charging for Wi-Fi

Since everyone has unlimited data plans these days, most regular customers don't really need Wi-Fi. If we offer the first hour free and charge an hourly fee after that, we can allow people doing quick tasks while effectively filtering out those who camp out to study using the internet.

2. Charging for power outlet usage

Laptops, not just phones, can easily last an hour or two nowadays. To stay longer, they'll need to charge. We could start charging for outlet use. It might be tricky to bill this by the hour, though.

Just these two things alone would stop most 'Kagong-jok' from coming.