* Foreign investors buy Indonesia, Thailand, sell Vietnam
* Thailand reverses gains to 33-month highs
* Singapore edges down; Malaysia bucks trend
By Viparat Jantraprap
BANGKOK, Aug 24 (Reuters) - Southeast Asian stock markets fell on Tuesday, with Indonesia's benchmark index coming off an all-time high, as investors cut positions in riskier assets ahead of U.S. economic data.
Late selling pulled markets off intraday highs. Singapore's main share index inched down 0.1 percent, while Thailand reversed early gains. Optimism fueled by better-than-expected second quarter economy had pushed the Thai market to its highest in 33 months on Monday.
The Philippines dropped 2.3 percent, ending a five-day rise to a 2-½ year high, while Vietnam lost 3.01 percent to an 8-month low, with an outflow of $233,000 for the session, Thomson Reuters data show.
Bucking the trend, Malaysia inched up 0.2 percent, marking a new 2-½ year high.
In Jakarta, the main share index ended down 0.4 percent. Asia's second-best performer this year hit an all-time high of 3,145.12 in early trade but attracted light inflows of just $8.79 million on the session, Thomson Reuters data show.
Among underperformers, PT Unilever Indonesia Tbk, a consumer goods company, dropped 2.7 percent, while PT Astra International Tbk, an automotive manufacturer, lost 1.5 percent.
Bangkok-based KGI Securities strategist Rakphong Chaisuparakul said investors in Bangkok adopted a wait-and-see approach ahead of key U.S. data including July existing home sales.
"The consensus is expecting sales at 4.72 million units, falling 12 percent month-on-month. Any disappointment in the release would likely intensify the risk aversion and weigh on risk assets," he said.
Bangkok recorded seven straight sessions of inflows to Tuesday for a combined $211 million, reversing the outflows having plagued the market seen since the middle of May.
Profit taking hit big capitalised stocks, with PTT Pcl down 2.3 percent, Siam Cement Pcl off 0.7 percent and PTT Chemical Pcl 1.9 percent lower. Their recent gains came after signs of a resolution to the Map Ta Phut industrial estate environmental row.
Broader Asian stock markets fell while U.S. stock index futures pointed to a sharply lower open on Wall Street on Tuesday. The MSCI Asia ex-Japan index had fallen 1.2 percent by 0916 GMT and U.S. stock index futures were down 0.72 percent.
The recent rally in emerging Southeast Asian stocks had made the region among Asia's top performers this year, including third-ranked Thailand, number-four Philippines and the fifth-best Malaysia.
Foreign funds are pouring into local currencies, bond markets and stocks, causing a broad rally in all as the region's growth momentum stands in stark contrast to the struggling developed world.
Emerging market bond funds extended their year-to-date record inflows to $32.8 billion, which trounces the previous full-year record inflow of $9.7 billion set in 2005, according to EPFR Global Fund Data dated Aug. 23.
All emerging market funds combined extended their year-to-date inflow gains to $34.5 billion after attracting $2.2 billion of fresh money in the latest week, the EPFR data showed. (Editing by Jason Szep)