Flood defences protecting the Thai capital are holding up, but the advancing waters that have swamped the inland still threaten to engulf Bangkok in a disaster that has claimed 300 lives. Thailand's worst floods in decades have inundated huge swathes of the kingdom, swallowing homes and businesses, shutting down industry, and forcing tens of thousands of people to seek refuge in shelters. Authorities are battling to protect the capital which is ringed by defensive walls that have so far largely prevented major flooding. But their efforts have left areas outside the city to bear the brunt of the rising waters. "The Thai government will do everything it can to help reduce the suffering of people from the floods and I hope everyone will join together so that we can get through this difficult time," said Prime Minister Yingluck Shinawatra. A large volume of water is bearing down on Bangkok, and a seasonal high tide is expected to make it harder for the flood waters to flow out to sea. In an attempt to speed the flow through waterways towards the Gulf of Thailand, authorities have organised around a thousand boats to line up with engines running on the Chao Phraya, Bang Pa Kong and Tha Chin rivers. Yingluck, speaking from the banks of the Chao Phraya in Nonthaburi province, north of Bangkok, said the boats' propellors would move only a relatively small amount of water but that the measure was still "worthwhile and efficient". Sandbags have been piled alongside waterways and authorities have been dredging and draining canals to allow more water to flow through, as well as diverting water to areas outside the sprawling city. Conditions in Bangkok remain mostly normal and Suvarnabhumi Airport -- the capital's main air hub which has floodwalls several metres high -- was operating as usual. Thunderstorms and heavy monsoon raised caused minor flooding on roads in the centre of the capital over the weekend, but the authorities have said they are confident they can prevent serious inundation in the low-lying city. Homes and businesses in inner Bangkok have been fortified with sandbags in preparation for possible inundation, and many residents have stocked up on food, water and flashlights. The floods, several metres deep in places, are currently affecting about one third of Thailand's provinces and have left at least 297 people dead. The United States sent a military transport aircraft from Japan carrying thousands of sandbags and 10 US Marines who are part of a survey team to assess how to help Thailand cope with the flooding, the US embassy said. The floods have dealt a heavy blow to Thailand's economy, disrupting production of cars, electronics and other goods. Japanese automakers including Toyota have suspended production in the kingdom due to water damage to facilities or a shortage of components. A fourth major industrial estate has been inundated in Ayutthaya just north of the capital after the floodwalls were breached, prompting an evacuation of employees.