however, as far as i know, they ask for original copy, is becasue that if the pr is approved, they need to chop on the passport (usu. the last page) and write down something. so if no orignal, where can they chop your pr status?
maybe you can call and provide them with some materials in order to pursuade them procced your application first ( am not sure if there is the danger of being reject, think it over)
1, the passport photocopy & scan copy
2, the photocopy & scan copy of the air ticket on when the passport holder will arrive singaproe
3, a sincere letter co-signed by main applicant & passport holder on your
4, all the other required documents ica asks for (the full set)
not sure if it helps, but anyway, it is not difficult to apply nowadays, wish u good luck