* HSI -0.7 pct, H-shares -0.4 pct, CSI300 +0.6 pct
Muted volumes as investors watch for post-plenum policy direction
* Boyaa surges on HK listing debut, but retail sell into rally
* SJM sinks after Q3 earnings disappoint
By Clement Tan
HONG KONG, Nov 12 (Reuters) - China shares pared early gains in choppy trade on Tuesday, with Hong Kong markets on the defensive in low volumes as investors awaited the outcome of a key four-day Communist Party policy meeting later in the day.
Huishang Bank Corp and Boyaa Interactive made contrasting listing debuts in Hong Kong. Huishang was flat, but Boyaa shares jumped as much as 30 percent after demand for its initial public offering was more than 832 times oversubscribed.
By midday, the CSI300 of the leading Shanghai and Shenzhen A-share listings was up 0.6 percent, while the Shanghai Composite Index rose 0.5 percent as midday volumes lingered near multi-month lows.
The Hang Seng Index shed 0.7 percent to 22,905.8 points, while the China Enterprises Index of the top Chinese listings in Hong Kong slipped 0.4 percent. Losses so far pared a strong late rally on Monday.
"The focus today is still very much the outcome of the plenum meeting. In such low volumes though, it is quite the ping pong market with any price moves exaggerated," said Jackson Wong, Tanrich Securities' vice president for equity sales.
China's leaders will unveil a reform agenda for the next decade later on Tuesday, seeking to balance the need to overhaul the world's second-largest economy as it loses steam with preserving stability and to reinforce the Communist Party's power.
Ahead of the official communique, trickles of possible changes appeared in various official newspapers in the mainland.
Some Chinese ship builders were buoyed by a report in the official China Securities Journal that Beijing will lower thresholds on subsidies to encourage companies to scrap older vessels. China Shipping Development climbed 1.1 percent in Hong Kong and 0.2 percent in Shanghai.
Mobile game developer Boyaa was a standout outperformer on its listing debut, although Tanrich's Wong said his retail clients sold into the rally after raising $127 million and attracting strong retail demand.
Other Chinese mobile gaming counters were mostly weaker. Kingsoft shed more than 2 percent, while NetDragon dived 3.6 percent and Forgame tanked 5.3 percent.
Huishang Bank, the second Chinese regional lender to debut in Hong Kong in just over a week, was flat in Hong Kong, but marginally outperformed the Chinese banking sector after weak money supply and total social financing data.
Industrial and Commercial Bank of China (ICBC) shed 0.8 percent in Hong Kong, but its A-share listing eked out a 0.3 percent gain with the Chinese banking sector broadly higher in the mainland.
Tuesday's weakness in Hong Kong though trimmed gains from a late rally on Monday, which some traders attributed to a China Daily story that China will allow private investors to buy up to 15 percent in state-owned enterprises -- but China's supervisory body for SOEs denied the story late on Monday.
There were also losses for Macau casino operator SJM Holdings, down 4.5 percent after underwhelming third-quarter profit growth also triggered a rating downgrade by a notch to "neutral" by JP Morgan analysts.