Farmers in Thailand's rice-growing Suphan Buri province are becoming increasingly desperate for water to irrigate their parched fields as the nation, a leading producer of the staple food, suffers its worst drought in more than a decade.

The wet season is under way, but Thailand is contending with drought conditions in seven out of 67 provinces, according to the National Disaster Warning Center, and water rationing is taking place in almost a third of the country.

Farmers have been asked to delay planting their main rice crop until August.

As a result of the drought, the Thai government lowered its forecast for this year's main-crop rice output by more than 2 million tonnes, according to a report this month by the Office of Agricultural Economics.

Out of desperation, farmers in the central province of Suphan Buri, 103 km (64 miles) from Bangkok, are fighting over the Tharakam canal, a small waterway that has not previously been used for irrigation.

"All our crops are dying and this is our last resort," said rice farmer Chanate Dangdumrong, 67.

The canal has pitted locals against each other, with people in the province's Don Jedi district accusing villagers upstream of hoarding its precious water to save their crops.

"They blocked off the water flow in the Tharakam canal so they can pump it all for themselves," said Kasem Laosittiwarong, 49, also a farmer.

Government requests to stop unauthorized pumping of canals are unrealistic and water rationing is unsustainable, farmers say.

A drop in output could underpin benchmark Thai prices, which are near their lowest since January 2008 amid an overhang of stocks built up under the previous government's rice-buying scheme.

In June, Thailand's finance minister said drought could cut economic growth by 0.5 percentage point this year.

The scheme, introduced in 2011 by the government of then-Prime Minister Yingluck Shinawatra, bought rice from farmers at above-market prices. Despite its popularity among producers, it backfired and cost the country billions of dollars in losses.

Thailand's junta, which took power in a May 2014 coup, has tried to step back from a culture of subsidies across the agricultural sector, but that has left some farmers disgruntled.

The government forecasts rain in drought-hit regions by August.

Farmers in Suphan Buri, including Chanate, fear the worst.

"This (canal water) may last us until the end of the month," he said. "If it doesn't rain by then - everything dies."