By Poppy McPherson and Chayut Setboonsarng UTHAI SAWANG, Thailand (Reuters) – The ex-policeman who went on a killing spree at a Thai daycare centre had risen quickly through the ranks of the police force in the capital, before a transfer to the provinces led to his use of drugs, and an abrupt halt to his career, police said. No clear motive had been established yet for the rampage on Thursday. But police said their preliminary investigation indicated Panya Khamrap was deeply troubled by marital and money problems following his suspension from police duty in January, after he admitted to using …