Receive threats to remove cabinets from apartment if work not paid up

I would've broken the job into several phases. That way if you weren't happy with one phase, you could've stopped at that time. $6500 is a huge amount to contract at one time in Vietnam. The possibility of something going wrong was enormous. You also needed to get everything in writing in both languages, perhaps supported with drawings and lists of materials. It sounds like a large amount of the specifications were verbal. That in itself was an invitation to disaster.
You are at an extreme disadvantage from square one because of your non-citizen status. You knew the contractor would receive preferential treatment from the legal system and so did the contractor.
How much have you paid? I couldn't find that anywhere.

I did contract electrical engineering for 35 years. The best way to not get screwed is by getting incremental payments against well-documented goals.

It's my experience that lawyers just make the problem more expensive. You might visit with one just to find if you have any rights at all, and that's it.

After lawyer fees your probably better off just to pay the 5 mil. I understand you don't want to pay it on principle, but you are a foreigner in a foreign country and you're not likely to get any justice here even with a lawyer.

Why do I get the funny feeling you are not the offended party in this transaction? From what I can tell, you have paid nothing for a huge amount of work. And are you leveraging their hope to get paid against some petty details, hoping for a discount? I too have been owned by my own monies.

We are only hearing one side of this argument.

Thou doth protest too much.

FWIW, I would not just [i]talk the talk[i] but hurry and deposit those 16,000.000 VND.

TBH, I have no pattience for people who owe me money and talk and promise but never actually do make payments.

Next, it will be down to $ 120. 

While I fail to understand the technical issue (there are potent anti mold chemicaals in small bottles available overseas), get it over witth.

Withholding the 16 million is a bad move. In the U.S., you might face a mechanic's lien against the property.

After half a year of construction I have to state in consternation that you must be lucky to find good craftsmen in Vietnam (only about 30% good craftsmen and vendors in our case) . The problem is not mainly a lack of skill but a lack of interest in everything.

It's not only the lack of work but also the disrespect for other people's property. 
As examples of many: We received handmade real wood furniture (we were lucky with this craftsman, in contrast to the OP  ). A craftsman who had to repair something at the house put a wet drink cup on such a piece of furniture and ruined it before we could use it for the first time.
Unmotivated craftsmen who had to repair something left a completely dirty wall behind.  Etc.

If you say that you will not pay the remaining amount before the defects have been repaired, they will be repaired. But the result is still poor.

You simply have to accept that the quality of craftsmanship in Vietnam is far below Western standards.

I am only happy when the craftsmen leave the construction site. Then I will repair the defects myself or hire someone to do it for me.

The few million dong I lose are not worth it to me to deal with unmotivated craftsmen.

What have I learned?
Buy the cheapest available, because the most expensive is not much better.

Andy Passenger wrote:

After half a year of construction I have to state in consternation that you must be lucky to find good craftsmen in Vietnam (only about 30% good craftsmen and vendors in our case) . The problem is not mainly a lack of skill but a lack of interest in everything.

It's not only the lack of work but also the disrespect for other people's property. 
As examples of many: We received handmade real wood furniture (we were lucky with this craftsman, in contrast to the OP  ). A craftsman who had to repair something at the house put a wet drink cup on such a piece of furniture and ruined it before we could use it for the first time.
Unmotivated craftsmen who had to repair something left a completely dirty wall behind.  Etc.

If you say that you will not pay the remaining amount before the defects have been repaired, they will be repaired. But the result is still poor.

You simply have to accept that the quality of craftsmanship in Vietnam is far below Western standards.

I am only happy when the craftsmen leave the construction site. Then I will repair the defects myself or hire someone to do it for me.

The few million dong I lose are not worth it to me to deal with unmotivated craftsmen.

What have I learned?
Buy the cheapest available, because the most expensive is not much better.

Most of the work done here is not by a person who has gone to college or done an aprenticeship. Most of the workmanship is below par.