Major Southeast Asian stock markets mostly closed lower on Thursday, led down by commodity-related stocks as a gloomy outlook for demand growth and the euro zone's spreading debt crisis hit oil prices. Thailand's benchmark SET index fell 1.3 percent to 1,172.92. Malaysian shares ended down 0.7 percent to 1,623.91. The Philippine index posted a modest 0.18 percent loss. Singapore's Straits Times index bucked the trend, advancing 0.5 percent.