The index closed 13.38 points lower after losing 8.24 points on Wednesday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) fell by 6.8% to VND20.23 trillion ($851.95 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 24 tickers dropped.
MSN of conglomerate Masan Group plunged 5.7%, followed by BID of state-owned lender BIDV with a 3.5% decline.
GVR of Vietnam Rubber Group lost 3.2% and BCM of Becamex Investment and Industrial Development closed 2.8% lower.
Three blue chips gained.
VIC of private conglomerate Vingroup went up 3.2%, while GAS of state-owned Petrovietnam Gas closed 1% higher.
Foreign investors were net sellers to the tune of VND342.33 billion, mainly selling MSN and VPB of private lender VPBank.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 0.80% while the UPCoM-Index at the Unlisted Public Companies Market was down by 0.75%.