Nearly 105,000 stock trading accounts were opened in May, the highest number since last September and four times that of April, according to the Vietnam Securities Depository.
It was also the first time the number of new accounts in a month had surpassed 100,000 since September.
The VN-Index gained 3.3% in May to finish at 1,075.17 points.
Investor confidence has improved in the past few months after the State Bank of Vietnam slashed interest rates three times.
Vietcombank Securities Company expects rates to drop further.
The number of new securities accounts was the highest ever in May and June 2022 when over 450,000 accounts were opened before a relentless decline began.
Starting in mid-2022 the VN-Index fell from its peak of over 1,500 points following some high-profile arrests for alleged stock manipulation including that of former FLC chairman Trinh Van Quyet and Louis Holdings chairman Do Thanh Nhan.
Earlier this year the number of new accounts fell to less than 30,000 a month.