Koh Ngai doesn't have a "pier", so your check-in point is going to be at the Koh Hai Fantasy Resort & Spa which is easily spotted. Make sure that you are at the ferry check-in point at least 45 minutes prior to departure.
Simply show the ferry staff your printed e-ticket, and the ferry staff there will replace it with a sticker that you should wear for your ferry trip. Because there is no pier on Koh Ngai, local longtail boat operators will transport you to your awaiting high-speed ferry that will be sitting just offshore. This is normal, so don't worry - it makes your arrival that much more interesting and exotic. The boarding process should be very easy from there, so sit back and enjoy the ride!
Address : Check in point: Koh Hai Fantasy Resort & Spa, Koh Ngai.