Don't think Singapore practises double jeopardy when it comes to CP. But he will go to jail anyway because he skipped military service.
This is what Singapore online media had to say about him.
*He will risk arrest if he ever returns to Singapore because he skipped NS.*
*Therefore if you are subject to the Enlistment Act and have not fulfilled your NS liabilities, the Government may withhold your renunciation of citizenship, i.e you are still considered to be a Singaporean and will have to serve NS.*
He will be charged for avoiding NS or military service anyway.
Seeing how he is still described as a "Singaporean", he has yet to renounce his citizenship. You'd think he would try to apply for US citizenship after being an asylee for over a year.
However, under Singapore laws, he will only be able to renounce Singapore citizenship if he takes up citizenship in another country and if hits 21 years old. (Yee's 21st birthday is at late October 2020)
Furthermore, most males complete their military service when they are 21. This means it is usually not possible for Singaporean males to renounce their citizenship without completing their military service.
Long story short not yet a US citizen, not 21, haven't completed military service, Yee is still a Singapore citizen even if Yee doesn't want to be one.