Generally, it is relatively easy to extend the visa for your longer stay in Vietnam at present through a travel agency. Renewal for the first time may cost you about 25-30$ (including a handling fee) and takes 03 working days to process (Monday to Friday).
The maximum period you can ask for is 30 days and it costs the same whether you ask for 1 day or 30 days. A second 10-day extension is possible at a cost of around $35-40. For this second extension you will be asked to show an air ticket dated after the expiry of your visa.
Not more than 15 days: for citizens of South Korea, Japan, Russia, Sweden, Norway, Denmark, Finland.
No visa required for travel less than 90 days or several visits within 6 months: Citizens of France holding valid diplomatic or official passports.
No Vietnam entry visa required for travel less than 60 days: APEC Business Travel Card (ABTC) Holders from Asia-Pacific Economic Cooperation (APEC) member economies.
No visa required for Vietnamese overseas less than 90days staying if holding Vietnam visa exemption certificate.