I had traveled to many South-East Asia countries including Thailand, Malaysia, Singapore, Hongkong, China, Laos, Macau...In most of the countries, people speak good English except Laos. Vietnam is developing fast and quickly conduct world integration so the need to improve English for people are very high. They need a lot of teachers.
There are some advantages that teacher have.
1. Easy to find job: many Language Centre
2. Food and Accommodation is cheap
3. Traveling is cheap
4. Teachers are very respected in Vietnam

For those who want to get job in Vietnam, can search for some Centre such as
Appolo Centre, British Council, Languge Link...