BAMBOO !!

"Bamboo has been identified as a sustainable housing construction material, both internationally and within other Habitat for Humanity affiliates in the Asia-Pacific region. Despite the benefits of using bamboo for houses, many people in Vietnam do not view bamboo as a first-choice construction material. Yet, in rural areas particularly, there are few alternative construction materials available to the locals."
ewb link

So building with bamboo is a definite research topic to consider...

Bamboo links:

wikipedia

Good points about Bamboo:
"Bamboos are some of the fastest growing plants in the world." -wikipedia
Cheap
local to Vietnam
Strong !!

The_Mechanical_Properties_of_Bamboo
youtube: Bamboo scaffolding across asia
youtube : bike made of bamboo

Bamboo structures
Floating bamboo restaurant

High end manufactured (pressed) bamboo modular components.
http://thebamboofactory.com/ (too expensive?)

Entire school made from bamboo
http://www.greenschool.org/

Bamboo Design and Construction:
http://bambooroo.net/about_bamboo.php

general botany:
Vasculur Bundle - the anatomy of xylem and pholem
http://en.wikipedia.org/wiki/Vascular_bundle

Bad points about bamboo:
long term use could make it rare and disrupt the environment
bamboo is probably home to may insects and animals.
Bamboo needs to be treated with 'Borax' to make it pest resistant

treating Bamboo for pest-resistance
http://bambooroo.net/about_bamboo.php

borax - treating agent:
http://www.earthclinic.com/Remedies/borax.html