Top 7 in Top 12 Code of Conduct on Vietnamese dining tables.
You must have at least one drink or alcohol when food is still full in your mouth. This "natural" habit sounds normal, but it shows the rush and is not polite in how it behaves. Food scrapers can be adhesive on water glasses, causing hygiene and lack of aesthetics.
Moreover, most people use alcohol when eating rice with the purpose of enjoying. The unreasonable combination of food and wine mixture will take away the spirit of the whole meal.
The habit of talking with food is unpolite behavior and makes it difficult for others to hear the content you want to say. So you need to eat out of rice and say what you want right after.