South Korean men are required to complete at least 21 months of military service before they turn 28, meaning Son can play abroad until July 2019, although there have been examples of delays and exemptions being granted.
Current conscription laws stipulate that athletes and sportsmen who win medals in the Olympic Games or gold medals in the Asian Games are handed exemptions but are still required to do four weeks of basic training.
Son, however, was part of the South Korean football team that suffered a heartbreaking quarter-final defeat to Honduras at Rio 2016 and missed out on a medal.
That means the last chance for Son to earn a guaranteed exemption is to help South Korea win the 2018 Asian Games. The tournament runs from August 18 to September 2, meaning he would miss the move into Tottenham’s new stadium at the start of the 2018/19 season.
Should Son be called to fulfil his military service, it is highly unlikely he would be a ‘soldier’ with most professional footballers instead playing for the military team.
Such is the sensitivity of the issue in South Korea that Son will not answer questions about military service and it is hard to get information from his home country where the laws regarding conscription constantly change.
It means that while Spurs are well aware of the rules, the club are largely in the dark over whether or not the military service is likely to be completed while he is their player.
While he would not relate the subject to military service, Son admitted that it was a huge blow not to win a medal at the Olympics with South Korea.
“It is true that after the Olympics I was very upset,” said Son. “I was really down because my heart was already in it for six months beforehand, but after the Olympics I thought ‘now I have to focus on the season’.
“It was not easy for everyone, but my family and my team-mates helped me a lot and made me feel stronger than before.”
Tottenham considered selling Son after he told the club he wanted to leave this summer, but a meeting with manager Mauricio Pochettino convinced him to stay and the decision has paid off for both parties.
“I want to play every game, this is normal,” said Son. “Every player is the same. I’m really happy to stay here and play in the Premier League and Champions League. For every player it is a dream to play in the Premier League and Champions League, so it is a dream come true.
“I had pre-season and I feel really fit. We played four games at the Olympics. I feel very fit. It is true I am in great form and have made a great start, but I have to keep working hard so I finish like this.”