I am studying abroad for 6 months in South Korea but I want to go to Cambodia to do a volunteer trip for two weeks at the end of school. However during the Cambodia program my student visa ends in the middle of the two weeks in Cambodia. My return flight to the USA is from South Korea. I may also have to stay the night at a hotel once I get back to South Korea, if I get back early (so I will need to leave the South Korean airport).
Can I fly to Cambodia and back to South Korea for a night with these problems to catch my flight home the next day without issues? Will the 90 days visa take the place of the student visa when I go back? Do I need to do something special? I will only be in South Korea for a night so I don't want to accidentally get in trouble.