Vietnam visa extension is much depending on your types of visa, purposes of visit, so we suggest that you contact the Immigration office of Vietnam for the visa extension advice.

Vietnamese Department of Immigration is located at 40 Hang Bai Street, Hanoi and 161 Nguyen Du, Ho Chi Minh City. You also can dowloand visa form extension online:

(http://xnc.congan.com.vn/vietkieu-nuocngoai/bieumau-vietkieu-xnc/mldocument.2008-04-24.7891982088/view)