You cannot have both. You are on a PGWP which is not a LMIA exemption under the links provided. You say you have LMIA exempt job offer, so your employer would have filed and been approved for one. You would have a LMIA exempt number so get that from your employer. You need a LMIA exemption from your employer and then on the LMIA exemption you need one year of Canadian work experience to count the 50 points. Depending on your NOC and/or whether Canada/Vietnam have a FTA with a job agreement listing your NOC, I don’t know if your job is eligible.I'm actually on PGWP and haven't left Canada for 4 years. I think have both PGWP and LMIA-exempt job offer
So unless you got the LMIA exemption approved a year ago, you cannot count 50 points.