Foreign income (dividend) while on a business visa

Someone told me that foreign income for non VN citizens is exempt from tax. However when I started looking for it I couldn't find any information regarding this.

If I would get a business visa and rent an apartment for 6 months, will I have to pay taxes over any dividend I receive from my offshore company and if so, how much?

It's actually a lot harder to establish legal residence in Vietnam than simply renting an apartment.  If your dividends are directly deposited into either your brokerage account or a bank account in your home country, I don't see how Vietnam could even know about them, let alone tax them.

Thanks for your quick reply THIGV. I must admit I haven't looked into great detail in the requirements for tax residence in Vietnam. It is just that someone pointed me towards Vietnam when he heard I was paying for Malaysian residence.
And I have no doubt Vietnam will never know about any offshore income unless I told them, but legally I'll have to pay tax in my country of residence, so I would rather tell them if the tax rate is 0% anyways (which I doubt from what I've been reading so far).