Thank you very much for checking my post.

I would like your helps regarding my working visa and arrival to Switzerland.

Recently, I have a new job at a Multi-national Company in Switzerland, and I have already received the working visa last month.

The problem is the starting date of my new job which is Dec 1st, the same day as issued in my Visa (From Dec1st).
I am confusing. Firstly, the HR of my company told me that this is very normal situation for who obtaining the working visa (started visa date = the first day of the contract) and I can enter Switzerland 1-2 days before Dec1st (ex. 28 Nov), however, today I have checked with the embassy in my country and they told me that I can not enter before Dec1st, according to my visa status on their system.

Confusing. I contacted my company again today, then they still confirm that the immigration authority will let me enter a few days before Dec 1st.
Honestly, I am worried about this if they are wrong, I will have a very big problems..

Any suggestions or experience?

Note that, I will fly from Asia to Vienna fro transit to Geneva. Does the immigration take place in Vienna? Are they going to understand my situation?

Thank you very much for your kindness

You can enter the country legally only from the date specified in visa. If you come 1-2 days before, you will be send back immediately on the next flight to my knowledge.

Yes the passport control would take place in Vienna. I don't think you can enter Switzerland or the Schengen zone(Vienna) before 1st of December.
I'd rather trust what the embassy says.

what is your nationality?

Thank you very much...

My nationality is Thai, but I live in Japan now.

I have bought the tickets... I think I will have a big problem now.. hmm....
any more suggestions?

Contact the local swiss embassy and try to change the dates (which is unlikely to happen). That is the only option now if you want to come before Dec 1.