Dear Lam 
��
You can visit website of 
basao.com for searching administration map of Vietnam in map scale 1/100.000 . They also have Vietnam map in larger scale but you have to contact directly with them. 
 
��
Could you contact directly with some Institute of VAST, they also have above map sources. 
��
Good Look 
��
Best regards 
��
-- 
T���ng Ph�����c Ho��ng S��n
Head of GIS & Remote sensing Department
Add: 01 Cau Da - Vinh Nguyen - Nha Trang City - Khanh Hoa Province - Viet Nam
Tel: 84-58-590553
Cell phone: 84-914176020