Most major Southeast Asian stock markets fell on Friday as investors booked profits a day after a rally on easing concerns about an imminent Fed rate hike, but Thai retailers outperformed after a plan to maintain the value-added tax rate.   Late buying in shares such as Home Product and Big C Supercenter helped trim losses in the broader market.  The SET index ended the day down 0.14 percent, with a weekly loss of 0.75 percent, its fifth straight week. Thai Deputy Prime Minister Pridiyathorn Devakula said on Friday the government plans to keep the value-added tax at 7 percent for another year from the end of September to support the economy.   Malaysia and Indonesia retreated but still ended the week up 1.2 percent and 0.3 percent, respectively.  The Philippines closed nearly unchanged after early losses, with a weekly rise of 0.1 percent. Vietnam closed up 0.3 percent on the day, declining 1.8 percent on the week.   Asian stocks dipped as Federal Reserve-inspired gains petered out.  The Fed on Wednesday opened the door further for an interest rate hike but signalled a more cautious outlook for U.S. growth, cooling speculation for tightening in June.   Bucking the trend, Singapore was up 0.8 percent, advancing 1.5 percent on the week.  Shares of Noble Group jumped 3 percent after it said Prudential Plc has increased its stake in the company to more than 5 pct and become a substantial shareholder