Visas are often confusing for people considering teaching English in Vietnam. Basically there are two types: 3-month tourist/business visas and 12-month working visas.
Most nationalities can get a 1 or 3 month tourist or business visa before or on arrival into Vietnam. Before you come you can send your passport to your local Vietnamese embassy with the correct forms and photos for a visa or you can get one on arrival. For a VOA you will need to buy an invitation letter online ($20 and up depending on duration/purpose) to submit along with the arrival form and a passport photo at the airport before customs. You also need to pay a stamping fee in USD on your arrival so bring change and be prepared to wait for the stamping process which can take up to an hour at peak times.
Europeans can get 15 day free VOA and US citizens get a (mandatory) 1 year tourist VOA.
When your visa is due to expire you can extend some kinds or get a new visa by re-entering Vietnam. With so many tempting Asian countries just a bus or short plane ride away it’s a cheap, fun trip anyway. Check online for the most up to date information on visas for your nationality and chat to the guys in the house for recommendations.
Some schools can provide you with a working visa, for this you need a university degree, police clearance and a TESOL/TEFL/CELTA/DELTA. These teaching courses are offered online and in class overseas as well as in Vietnam. Employers prefer an in class acquired qualification but any one of these courses will help prepare you for what to expect and give you a good idea of how to teach to different students.
TESOL-Teaching English to Speakers of Other Languages
TEFL-Teaching English as a Foreign Language
CELTA-Certificate in English Language Teaching to Adults
DELTA-Degree in English Language Teaching to Adults