I'm sorry to say, you will be denied boarding.
I've learned this the hard way, forcing a transit in SIN during the pandemic.

This may depend on the airport pax flow, but by default please expect to be steered to the passport control. Connection usually sits after passport control. ICN experts could know better.

And you just explained you cannot clear passport control.
I would strongly advise to rebook your tickets if you can.


I will be extremely surprised if boarding crew would allow you to embark.

Please share the outcome.

Good luck!