Can an American ex-U.S. Navy sailor join the Singapore military?

I was in the United States Navy and I want to know if I can enlist in the Singapore military? Do I have to become a citizen to join? Or can being a permanent resident is good enough? If permanent residency is required at minimal, then how do I get permanent residency? Also, I've had pain in my knees for the... show more I was in the United States Navy and I want to know if I can enlist in the Singapore military? Do I have to become a citizen to join? Or can being a permanent resident is good enough? If permanent residency is required at minimal, then how do I get permanent residency? Also, I've had pain in my knees for the past 2 years, but haven't done surgery or anything to it. Would that disqualify me from doing Singapore National Service? I am deeply willing and would do anything to serve the Singapore military!

Also, I completed 4 years of Army JROTC (Junior Reserve Officer Training Corps) in high school, so I have plenty of military and leadership knowledge, if that helps.
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