There is a terror alert issued by the U.S. embassy in Thailand for U.S. citizens in Thailand. Since the Uyghers were sent to China, Uygher sympathizers may attack Thailand, especially areas of tourist concentrations. Maybe the Thai government is exercising a rare example of it being proactive with it's show of force at the festival. Making knowledge of a possible terrorist attack public would be too much to ask as it might hurt tourist numbers.