No buddy, you only need a letter from your wife if going to HCMC. No proof of funds for the multi entry, but be aware with this visa you only get 90 days permission to stay each entry, but with a bounce at the end you will get 15 mths + 1 mth extension from this style of visa.
More information is needed, was it a SETV, a METV, normally a SETV is only 2 mths (60 days) whereas a METV from his home country is 3 mths (90 days). Which is it?