* Shanghai stocks lower, blue-chip CSI300 index down
* Gains in Shanghai stocks led by Henan Taloph Pharmaceutical Stock Co Ltd and losses by Hubei Mailyard Share Co Ltd
* China's A-shares are at a 20.54 percent premium over H-shares
SHANGHAI, May 29 (Reuters) - Shanghai stocks posted a fifth straight session of losses on Tuesday, as investors became concerned about credit risks amid more bond defaults, while Beijing vowed financial stability ahead of shares being included in MSCI's global benchmark indexes.
** The blue-chip CSI300 index fell 0.8 percent to 3,804.01 points, while the Shanghai Composite Index closed down 0.5 percent at 3,120.46 points.
** China Energy Reserve & Chemicals Group Co (CERCG) said it failed to repay a $350 million bond that matured earlier this month due to a "tightening in credit conditions", the latest Chinese company to default amid a crackdown on financial risk.
** It is the latest in a wave of corporate debt defaults amid a broad government-led campaign to crack down on risky financing, and follows a reminder from China's securities regulator that exchanges should monitor default risks.
** "Before any changes in (Beijing's) policies, credit risks will continue to spread and more companies will face bond insurance failure or bond defaults, which in turn will continue to dampen risk appetite," Xu Biao, chief analyst, TF Securities, wrote in a note.
** For the moment, the core concern for China's market is the liquidity problem that could be triggered by credit risks, Xu added.
** A senior Chinese securities regulator vowed to maintain financial stability and prevent asset price bubbles as the country accelerates the opening-up of its financial markets to foreign investors.
** The inclusion of Chinese stocks in closely tracked MSCI share indexes is widely expected to draw tens of billions of dollars into the mainland market next month, but active fund managers' conservative positions could mean inflows are much smaller.
** Most sectors lost ground on Tuesday, led by a slump in pharmaceutical firms, as investors booked profits after a strong run-up in the past months.
** An index tracking major healthcare companies tumbled 4.9 percent, posting its worst day in more than two years. Industry bellwether Zhangzhou Pientzehuang Pharmaceutical plunged the maximum allowed 10 percent, after having gained more than 80 percent so far this year.
** Around the region, MSCI's Asia ex-Japan stock index was weaker by 0.58 percent, while Japan's Nikkei index closed down 0.55 percent.
** At 07:02 GMT, the yuan was quoted at 6.4151 per U.S. dollar, 0.28 percent weaker than the previous close of 6.3969.
** The largest percentage gainers on the main Shanghai Composite index were Henan Taloph Pharmaceutical Stock Co Ltd up 10.1 percent, followed by Jiangsu Lianhuan Pharmaceutical Co Ltd gaining 10.06 percent and CCS Supply Chain Management Co Ltd up by 10.05 percent.
** The largest percentage losers on the Shanghai index were Hubei Mailyard Share Co Ltd down 10.03 percent, followed by GuangDong GenSho Logistics Co Ltd losing 10.01 percent and Shanghai Wondertek Software Co Ltd down by 10.01 percent.
** So far this year, the Shanghai stock index is down 5.6 percent, the CSI300 also has fallen 5.6 percent while China's H-share index listed in Hong Kong is up 2.1 percent. Shanghai stocks have risen 1.24 percent this month.
** As of 07:03 GMT, China's A-shares were trading at a premium of 20.54 percent over the Hong Kong-listed H-shares. (Reporting by Shanghai Newsroom; Editing by Biju Dwarakanath)