The accepted style of dress for a business meeting in Vietnam is conservative - a dark colored, uncontentious suit and tie are customary for men. Women should wear conservative suits or dresses; a blouse or other kind of top should have a high neckline. Stick with subdued, neutral, colors such as beige and brown. Women must take care that their skirts are not above the knees; good quality jewelry that is neither ostentatious nor overly expensive, is recommended for making the right impression.
Flat shoes or very low heels are the main footwear options for women due to the emphasis on conservative, modest, dress in Vietnamese business culture, especially if you are relatively much taller than your hosts. High heels are acceptable only at a formal reception hosted by a foreign diplomat.
Jeans may not be acceptable casual wear for both men and women especially when you working with state company.