Your Mongolia police check from 2005 is not valid anymore. Police checks submitted with the application must be less than 3 months. So if you were 18 or over when you left Mongolia in 2005, you will need to get a new one from there.
You must also get a Vietnam police check.
There is no need for a Canadian check, as that is only done upon specific request from CIC.
http://www.cic.gc.ca/english/information/applications/guides/5289ETOC.asp#police_cert
You and your family members who are 18 years of age and older and are not permanent residents or Canadian citizens must provide:
valid police certificate, or
police clearance, or
record of no information.
These documents are to be provided for each country other than Canada, in which you have lived for six (6) consecutive months or longer since reaching the age of 18.
Note: If you or your family members were under 18 years of age (16 years of age in certain jurisdictions) for the entire time you lived in a particular country, you do not need to provide a police certificate for that country.
The certificate must have been issued no more than three (3) months prior to submitting your application. If the original certificate is not in English or French, then you will need to submit both the certificate and the original copy of the translation prepared by an accredited translator.