BANGKOK (AP) — Seasonal monsoon rains may worsen flooding that has already badly affected about a third of Thailand. A tropical storm swept through the upper part of the country over the weekend, causing flash floods that affected thousands. Disaster-prevention officials say 12 provinces along the Chao Phraya river, including Bangkok and the old capital Ayutthaya, should be prepared for new flooding as water levels increase in the Chao Phraya dam by 1 to 3 feet over the next few days. Soldiers helped fill sandbags in Ayutthaya. Flood gates and pumping stations were being operated carefully in Bangkok to try to mitigate any potential damage.