* HSI up 1 pct, climbs 3.8 pct this month
* CSI300 up 0.7 pct, but down 1.7 pct in October
* H-shares have best month in 9, outperform CSI300 for 5th month
* ICBC positive Q3 earnings buoys gains for ``Big Four'' banks
HONG KONG, Oct 31 (Reuters) - Hong Kong shares posted a second-straight monthly gain on Wednesday, bouncing off a near two-week low after Industrial and Commercial Bank of China (ICBC), the country's largest bank, posted third-quarter earnings that beat expectations.
The Hang Seng Index rose 1 percent on the day and 3.8 percent in October to 21,641.8. The benchmark is now down 0.8 percent from a 2012 closing high recorded last Thursday. It is up 17.4 percent in 2012.
The China Enterprises Index of the top Chinese listings in Hong Kong posted its best monthly gain in nine, up 7.6 percent in October after rising 1.2 percent on Wednesday. It is up 6.5 percent on the year.
In the mainland, the CSI300 Index of the top Shanghai and Shenzhen listings rose 0.7 percent, but was down 1.7 percent in October. The Shanghai Composite Index rose 0.3 percent, but lost 0.8 percent on the month. They are each down 3.9 and 5.9 percent on the year.
But gains in both markets came in weak turnover. Despite the Hong Kong Monetary Authority intervening late on Tuesday for a fifth time in less than two weeks to weaken the local dollar, Hong Kong turnover stayed weak, suggesting inflows could have yet to filter into the local stock markets.
``International fund managers are increasing their allocation to this part of the world, but there is little reason for investors to come back into the market now,'' said Hong Hao, chief strategist with Bank of Communications International Securities.
``We just hit new 2012 highs last week, but earnings haven't been fantastic, so we need new catalysts to breach the stiff chart resistance,'' Hong added.
That could come as soon as Thursday, when Beijing releases its official PMI at 0100 GMT. The report is expected to show factory activity accelerated in October to its fastest pace in five months, strengthening hopes that growth is recovering in the world's second-largest economy.
Still, offshore Chinese plays have outperformed onshore peers for five straight months.
The Hang Seng Index A/H premium index has now stayed under 100 for almost two weeks, suggesting the premium that onshore shares trade over their offshore peers is now reversed. On Friday, it hit its lowest intra-day level since June 2011.
According to a Reuters poll, Chinese fund managers slightly reduced their recommended equity weightings in October as investors remained cautious about China's economic outlook, days ahead of Beijing's once-in-a-decade leadership transition.
``BIG FOUR'' CHINA BANKS UP
On Wednesday, ICBC rose 2 percent in Hong Kong and 0.3 percent in Shanghai after posting late on Tuesday a better-than-expected 15 percent rise in quarterly net profit as interest margins widened due to increased demand for credit.
In Hong Kong, the other ``Big Four'' Chinese banks were also stronger. China Construction Bank (CCB) jumped 2.3 percent, Bank of China (BOC) gained 2.2 percent, while Agricultural Bank of China (AgBank) was up 1.5 percent.
But their smaller rivals were broadly weaker, in a sign that investors expect the Chinese central bank's rate cuts and the resulting narrowing margins will be more keenly felt by the smaller banks as they compete with the state-owned behemoths by offering cheaper loans.
In Hong Kong, Bank of Communications, China's fifth-largest lender, slid 2 percent despite posting a 12 percent rise in third-quarter net profit. China Minsheng Bank slipped 1.4 percent.
In a report on Wednesday, JPMorgan analysts downgraded Minsheng from ``neutral'' to ``underweight'' and BoCom from ``overweight'' to ``neutral'' while cutting their target price for BoCom by about 13 percent, expecting funding pressures and rising non-performing loans to challenge both banks' bottom lines.