Police warned students Friday to avoid street protests after a gunman shot and wounded two students demonstrating against Thailand's prime minister raising new fears of violence in the country's tense political crisis.  The attack came after Samak proposed a national referendum Thursday to decide his political fate, an unconventional compromise that was dismissed by critics as a stalling tactic that will prolong the unrest. About 100 students were marching to demonstrate outside of Samak's home late Thursday when an unidentified gunman on the back of a motorcycle opened fire on the crowd, said police chief Col. Somsak Bunsaeng of the Ladprao station in northeast Bangkok.  One of the students was shot in his left leg, the other in his left arm. Police said they were hospitalized but were not seriously hurt. Anti-government protesters have occupied Samak's official headquarters, Government House, for 11 days, vowing not to leave until he resigns.  Samak imposed a state of emergency Tuesday after his opponents and supporters clashed near Government House in rioting that left one person dead and dozens wounded. The decree gives the military the right to restore order, allows authorities to suspend civil liberties and bans public gatherings of more than five people.