After 14 months of construction, the runway's concrete pavement and taxiway have been largely completed, with contractors now focusing on drainage, service roads and other remaining works.
Installation of the runway's lighting system and equipment is scheduled to begin next month.
The 4-km, 75-metre-wide runway runs parallel to the first runway, with both designed to accommodate the world's largest commercial aircraft.
Built on a 5,000-hectare site in Dong Nai City, Long Thanh International Airport is intended to become Vietnam's largest airport and a regional aviation hub.
ACV said work is also progressing on the passenger terminal, internal roads and other aviation infrastructure. Trial operation of terminal equipment is expected to begin in September, ahead of the airport's planned commercial opening in December.