Transcript of the above video:

As the title of this video suggests, we are discussing the question "Does a Visa in and of itself guarantee the bearer entry to the country it is intended for use?" No, it does not. A Visa is not a guarantee of entry. A Visa is simply the authorization to essentially approach the gates if you will of that country and ask for admission.

I know that sounds like a semantic point but it is really not if you look at it from the standpoint of, it is essentially the right to travel to that country and then again Immigration Officers at a Port of Entry, Customs Officers as well or in the case of the United States, US Customs and Border Protections, they have kind of combined all of that, but Immigration Officers here in Thailand for example, or the United States, if they deem that person as a threat to National Security for example or some sort of, if they have overstayed in the past, they violated policies or laws in the jurisdiction in the past, they can say: "Look we are not going to admit that person. Visa or no Visa, we are done here." The Visa is revoked and be on your way and that is basically what you are stuck with. At the end of the day, essentially is yeah the Visa simply allows you to travel to that country but as far as entry into that country, that determination is made at the Port of Entry by an Immigration Officer. 

Now again, it is not overly common but I have done a number of videos about US Immigration where I had a client who actually witnessed somebody else being turned away at a border in the United States. It does happen here in Thailand especially those who have been on the Blacklist, prior overstays, things of this nature, Immigration has that Authority so don't view a Visa as a guarantee in and of itself of entry into a given country.