The index closed 38.35 points lower after gaining 3.94 points on Wednesday. It has fallen by nearly 37% this year.
Trading on the Ho Chi Minh Stock Exchange (HoSE) increased by 4.2% to VND10.83 trillion ($435.51 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 29 tickers dropped.
Eleven blue chips hit floor price, including CTG of state-owned lender VietinBank, HPG of steelmaker Hoa Phat Group, MSN of conglomerate Masan Group, MWG of electronics retail chain Mobile World and NVL of real estate developer Novaland Group, all closed 7% lower.
Some other major decliners were PLX of fuel distributor Petrolimex and TCB of the largest private lender Techcombank, both down 6.6%, and KDH of real estate firm Khang Dien House with a 6.4% fall.
No blue chip gained.
Foreign investors were net buyers to the tune of VND16.77 billion, mainly selling HPG and STB of Ho Chi Minh City-based lender Sacombank.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 4.47%while the UPCoM-Index at the Unlisted Public Companies Market was down by 4.71%.