eslHQ - Linking phrases

It's a bit odd in terms of meaning rather than position :

Meaning : As a result is a connective which links a cause to an effect - but here we seem to have...
Cause : advertising / Effect : dying - which clearly isn't logical.
Really the meaning is that there's a chain of causes/effects: Cause = advertising / Effect = more smoking ; Cause = more smoking / Effect = dying.
Also, you mention the effects on passive smokers - but they are actually "non-smokers" who you later say are not affected.

So I'd rephrase it as :

Smoking advertisements should be banned because they encourage smoking, and cigarettes harm the health of both smokers and passive smokers. As a result of this advertising, many people in the world smoke a packet of cigarettes a day or more and, consequently, they and the people who they associate with, die earlier than non smokers...

However, in terms of position (which is what you asked about), As a result (and other alternative adverbials such as consequently) are fine at the beginning of the clause - but should be followed by a comma.

Smoking advertisements should be banned because they encourage smoking, and cigarettes harm the health of both smokers and passive smokers. As a result, many people in the world who smoke a packet of cigarettes a day, and the people who they associate with, die earlier than they would otherwise.

Smoking advertisements should be banned because they encourage smoking, and cigarettes harm the health of both smokers and passive smokers. Consequently, many people in the world who smoke a packet of cigarettes a day, and the people who they associate with, die earlier than they would otherwise.

Alternatively, if placed within the sentence, they should be surrounded by commas (see consequently in the first example) :

Notice that I've also eliminated the word "so", just leaving "many". "so many " makes no sense here as it is over-emphatic.