YANGON Senior officials from six Asian nations Wednesday began mapping out strategies to improve cooperation in the war against drugs, against the backdrop of a brewing row between Thailand and Myanmar over the illicit trade. Representatives from Cambodia, China, Laos, Myanmar, Thailand and Vietnam were holding preparatory talks before their home ministers meet on Friday to approve new initiatives to close down the narcotics industry. The Myanmar hosts will then torch mountains of heroin and methamphetamines on Saturday in a ceremonial burning.