The Hanoi Stock Exchange, Vietnam’s second biggest, said it will require companies to set an initial share price on debut and limit moves to a maximum 30 percent from that level after “unreasonable” disparities between prices and value.

Companies seeking to list on the bourse will have to submit their proposed initial price for approval starting in May, the bourse said in an e-mailed statement on Monday (March 21). The rule will apply to listings on Hanoi’s informal “over-the-counter” market, known as UpCoM, starting in April, with price moves on debut limited to 40 percent, the exchange said.

Some investors have ordered shares at “unreasonable prices – too high or too low – compared with stock values, affecting the reference prices of companies in subsequent trading days, and that led to an erroneous reflection of the indexes,” the exchange said in the statement. There is currently no maximum move on debut. The daily limit is 7 percent after the first day.

Vietnam is seeking to improve its stock market’s image after the benchmark VN-Index dropped 2 percent last year, the second-worst performance among Asia’s 15 biggest markets. The State Securities Commission in December pledged a clampdown on securities fraud with increased surveillance after authorities started the nation’s first share-price manipulation prosecution.

“This is a good measure in the current environment,” said Phan Dung Khanh, research manager at Kim Eng Vietnam Securities Co. “It will help restrain share-price manipulation, especially when companies’ stocks are held by a group of people.”