* CSI300 +0.1 pct; SSEC +0.1 pct; HSI +0.9 pct
* Market price in some upside surprise in China's Q1 GDP
* Index of A/H share premium to fall for 7th day to a 5-month low
SHANGHAI, April 14 (Reuters) - China and Hong Kong stocks remained firm on Thursday morning, with investors pricing in some upside surprise in China's first-quarter GDP figures to be released on Friday, traders said.
Data released on Wednesday's showed China's exports in March returned to growth for the first time in nine months, providing an encouraging sign ahead of the GDP release.
By the lunch break, both the CSI300 index and the Shanghai Composite Index had risen 0.1 percent.
Hong Kong shares rose to three-month highs, with the Hang Seng index adding 0.9 percent while the Hong Kong China Enterprises Index gained 1.1 percent.
In a sign of rapidly shrinking price differences between the two markets, an index tracking premiums of China-listed firms to their Hong Kong-traded counterparts is on track to fall for seven sessions in a row to a five-month low.
"We believe the recent trade, car sales and electricity consumption data point to a potential upside surprise to March data," Morgan Stanley wrote.
"In the near term, we continue to expect a cyclical improvement as past stimulus measures are still filtering through to the economy."
The improving outlook for China's economy has increased investor appetite for risky assets.
An index tracking mainland investors' confidence in the stock market rose to 54.7 in March, up 12.1 percent from a month earlier, and exceeding 50 for the first time since December.
A reading above 50 indicates optimism, while figures below 50 signals pessimism.
The China market, which is under increasing pressure from profit-takers following a month-long rebound, also got some support from news that China's central bank will inject 40 billion yuan ($6.18 billion) into the money markets on Thursday.
Most sectors, including IT and consumer rose in both China and Hong Kong markets, but energy and resources shares dropped as investors took profit after Wednesday's surge.
Samuel Shen and Pete Sweeney; Editing by Simon Cameron-Moore