A 52-year-old Buddhist rubber tapper was killed Friday by a recently planted landmine in one of Thailand's troubled Muslim-majority southern provinces, police said. Two police officers were also seriously injured after they went to investigate the incident in Than To district of Yala province and triggered another landmine.The use of landmines appears to mark a new tactic by suspected Islamic separatists in three southern Thai provinces near the border with Malaysia where a raging insurgency has left more than 4,100 people dead in six years.