International Pavilion "ideally" is the main attraction of an expo and probably the biggest building inside the expo since it is composed of many countries' exhibits.
What to see?
Of course this will always depend on the time you have, your interests and if you're not tired of walking yet. If you happen to start visiting other pavilions then the tendency is that you get tired and probably just prefer to sit. That is why, I personally think you need 2-3 days to fully enjoy the expo. Anyway, back to the international pavilion, some popular country exhibits are Japan, Singapore, Thailand, USA, China, Australia, Russia. I based this on the long line of people waiting outside the exhibit rooms. Of course the line would also depend on the exhibit room schedules, since some country exhibits have short movie showings or have guides who would explain the things inside the room so they need groups as audience. On the other hand, there is no need to fall in line in other country exhibits. The International Pavilion is right in front of the gate from KTX Yeosu Station so you could start your journey with this pav.
Exhibit room sizes are also different. I don't know why but someone told me it depends on the country's budget. USA, Japan, China have relatively huge exhibit rooms than Malaysia's and Philippines.' "Architectural" designs are also impressive. For me France and Philippines have good interior. Thailand and Cambodia's exterior designs were amazing. It would make you want to get inside their exhibit. My personal favorite is Thailand. Even if you don't get inside yet, it has a big screen outside showing different sites of the country plus a talking "palace guard." There are also many stores and restaurants in the pavilion so you'll never get hungry.
The main reason why countries exhibit at the expo is nation branding. Since world expo is one of the biggest events for many countries happening in one place, together with sports events like Olympics etc. many countries invest a lot of money and effort for this event. So you can expect good and quality presentations. When you visit Yeosu Expo make sure you drop by at International Pavilion ^^
I'll be writing more about the other pavilions at Yeosu Expo in my next entries so stay tuned ^^