The index fell 0.36 points after declining 4.26 points Wednesday.
Trading on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, dropped 1.79% to VND16.55 trillion ($662 million).
The VN30 basket, comprising the 30 largest capped stocks, saw 16 tickers dropped.
BCM of Becamex Investment and Industrial Development fell steepest at 1.6%, followed by VRE of retail real estate arm Vincom Retail with a 1.4% decline.
TCB of the largest private lender Techcombank lost 1.2% and MSN of conglomerate Masan Group closed 1% lower.
Eleven blue chips gained, with BID of state-owned lender BIDV rising 1.9%.
Foreign investors were net buyers to the tune of VND43 billion, mainly buying VPD of Vietnam Power Development and TCH of real estate company Hoang Huy Investment Financial Services.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, gained 0.12% while the UPCoM-Index for the Unlisted Public Companies Market rose 0.29%.