Ron Corben BANGKOK — Thailand faces a crucial week in its long running political crisis, as fears of violence and civil strife have led to calls by senior security officials to tighten security. Thailand's caretaker government says it is stepping up security to prevent clashes between pro- and anti-government protests. Political tensions are rising amid anti-government calls for a neutral prime minister to be appointed. Department of Special Investigation chief Tharit Pengdit says calls for a non-elected head of government by the anti-government People's Democratic Reform…