By Chandini Monnappa Aug 30 (Reuters) - Thai shares hit their highest level in more than four years on Wednesday before erasing the gains to trade marginally higher ahead of the release of factory output and inflation data this week. Thailand's SET index rose as much as 0.8 percent to its highest since May 23, 2013 with energy and utility stocks leading the gains. Gas and petroleum company PTT climbed as much as 2 percent, Airports of Thailand rose 2.3 percent and Siam Commercial Bank climbed up to 2.4 percent to its highest since July 27. A Reuters poll showed annual headline inflation rate may have increased slightly in August and factory output likely expanded, developments that would ensure the central bank still has room to keep monetary policy loose. Thailand is scheduled to release its factory output data on Thursday and headline inflation numbers on Friday. Meanwhile, MSCI's broadest index of Asia-Pacific shares outside Japan rose half a percent, taking cue from Wall Street's higher close, as concerns about North Korea's firing of a missile over Japan ebbed. "Asian bourses may see some further stabilisation if not recovery today as the risk-off concerns fade a little," OCBC Bank said in a note. Among other gainers in Southeast Asia, Singapore shares rose half a percent with financials accounting for nearly half the gains. Oversea-Chinese Banking Corp was up 0.5 percent, while United Overseas Bank gained 0.6 percent. Meanwhile, Philippine shares fell with industrial stocks accounting for half of the losses. JG Summit Holdings fell as much as 2.4 percent, while Aboitiz Equity Ventures dropped more than 1 percent. For Asian Companies click; SOUTHEAST ASIAN STOCK MARKETS: Change at 0438 GMT Market Current previous close Pct Move Singapore 3265.74 3249.34 0.50 Bangkok 1614.61 1614.14 0.03 Manila 7916.17 7948.39 -0.41 Jakarta 5884.431 5888.212 -0.06 Kuala Lumpur 1760.87 1761.14 -0.02 Ho Chi Minh 776.44 774.03 0.31 Change on year Market Current End 2016 Pct Move Singapore 3265.74 2880.76 13.36 Bangkok 1614.61 1542.94 4.65 Manila 7916.17 6840.64 15.70 Jakarta 5884.431 5296.711 11.10 Kuala Lumpur 1760.87 1641.73 7.26 Ho Chi Minh 776.44 664.87 16.80 (Reporting by Chandini Monnappa in Bengaluru; Editing by Subhranshu Sahu)