BANGKOK, Sept 30 (Reuters) - Business owners in a province in central Thailand have been battling in vain to protect their stores from floodwaters. Video taken from a boat in the commercial areas of Nakhon Sawan, about 220 km (136.7 miles) north of the capital Bangkok, showed empty streets flooded with waist-high brown water that has breached shutters and sandbags, damaging restaurants and shops. At least seven people have died in floods over the past week that have affected 200,000 households in 30 provinces in the lower north and northeast. As of Thursday, 18 provinces were still dealing with floods. "I was prepared by protecting my stores with sandbags, but it still didn"t help at all," said Satharn Sae-Chua, a Nakhon Sawan business owner. Drone footage showed a city with no visible dry land, with commercial areas and vast stretches of fields and farmland submerged. Authorities have issued a warning to communities along the Chao Phraya river, which flows through Bangkok, that levels are expected to rise from Friday into next week. Bangkok Governor Aswin Kwanmuang said the city has contingency measures, while Prime Minister Prayuth Chan-ocha said waters should recede in 10-15 days, if there were no more storms. The government has said the situation is manageable with no repeat of the floods of 2011, which were the worst in 50 years, killing hundreds of people, damaging vast areas of farmland and paralysing Bangkok and its industrial belt.