Business 1 year visa

I am a retired consultant with german nationality and would like to move my residence to Vietnam around November 2017. In accordance to the visa section of embassy in Thailand (where I live at this time) I would be eligible to apply for a 1 year business visa. However, with this visa it is not clear to me whether I am subject to legal and tax obligations although I will not work in the country. Who could give me a hint?

You wont be liable for tax unless you legally work.