I just received an email today from CHC Singapore responding to an email that I sent 3 days ago. I guess I got lucky this time... :
The email replied to my query on PPR after my wife redid her med exam 2 weeks ago. In the email, CHC Singapore told me that my wife could submit her passport to IOM office in HCM City. I have to call Ms. Uyen later today to confirm that if the email from CHC Singapore is sufficient for my wife to drop off her passport because I know a PPR usually includes Appendix A and Appendix B which are just a template listing passport holders' names, addresses, and prefilled File Number which I believe CHC Singapore already had in their file. I hope everything will be fine.