I got my wife to print out a letter saying I was staying with her and our daughter. Got her to scan it with her ID card on the bottom and it was rejected.
Was told it needed to be hand written, still with her ID card on it.
Just flown this route with Scoot, stayed 3 hours in Singapore. Though I do have a Non O visa.
Overstay should not cause a problem. It’s only when you get picked up by police that they can then deport you.
As for coming back next day, that is down the IO. If he thinks you are living here and border bouncing to stay here, eventually they will ask questions