If you are a citizen of a Southeast Asian or Nordic countries, Japan, South Korea, you do not need a visa to enter Vietnam for tourism purpose. If your nationality is different from what was mentioned above, you can obtain your visa from the embassy or opt for visa on arrival.
The second option takes only a maximum of 2 days but it applies to air travel only.
For the former option, the Vietnam embassy address in Singapore is:
10 Leedon Park St., SINGAPORE 267887
Tel: (65) 6462 5936/ 6462 5938
Fax: (65) 6468 9863