The 27-year-old will miss the Swans' final Premier League game of the season at home to Manchester City on Sunday as he has been granted leave by the club.
South Koreans must complete two years' compulsory military service before the age of 29 or face being exiled, but after winning bronze at the 2012 London Olympics, Ki and his teammates' service was reduced to four weeks.
Swansea manager Francesco Guidolin said: "There is no Ki this weekend because of his military service. He has to do four weeks and we want him to have some more time for his holiday."
Ki is expected to be back at the club in time for the start of pre-season training at the beginning of July.