Thailand is to invoke a harsh internal security law for 10 days in central Bangkok to control mass rallies by anti-government Red Shirt protesters. Prime Minister Abhisit Vejjajiva said the measure will be enforced from Thursday in the city's historic Dusit district, where thousands of red-clad demonstrators loyal to ousted premier Thaksin Shinawatra plan to gather on Saturday. He said the Internal Security Act (ISA) will remain in force until October 25. The government has already decided to invoke the ISA for the upcoming summit of the 10-nation Association of Southeast Asian Nations and their six dialogue partners taking place in the southern resort of Hua Hin. The summit will be attended by the leaders of China, Japan, South Korea, India, Australia and New Zealand as well as ASEAN countries. It plans to mobilize an 18,000-strong security force at the meeting. <br/>