The two organizations offering the IELTS exam in Vietnam are IDP and the British Council.
IDP
http://www.vietnam.idp.com/ielts/registration_procedure.aspx
THE BRITISH COUNCIL
https://vietnam.ielts.britishcouncil.org/iorpsea/html/registration/showExamSessionListServlet.do
IDP
http://www.vietnam.idp.com/ielts/registration_procedure.aspx
THE BRITISH COUNCIL
https://vietnam.ielts.britishcouncil.org/iorpsea/html/registration/showExamSessionListServlet.do