Thailand's Royal Irrigation Department (RID/สทนช.) has issued an expanded flood alert (Announcement 3/2569) for Sept 11-13, warning of flooding, flash floods, and mudslides across 23+ provinces as a monsoon trough and southwest monsoon intensify. Heaviest rainfall recorded Sept 11 reached 141 mm (Sisaket) and 108 mm (Bangkok). Further heavy rains expected Sept 14-16 in central, eastern and southern regions. Current national water reservoir capacity stands at 69% (55.6 billion m³), but 9 major and 55 medium-sized reservoirs remain critically low (below 30%).