The government must closely work with neighbouring countries to improve the management of the Mekong River to reduce economic damage and loss of life during floods in the future, the International Rivers Network says.
Pianporn Deetes, campaign director for the Southeast Asia Programme at the International Rivers Network, said a huge volume of water from Myanmar contributed to the flooding disaster in Chiang Rai province.
Currently, there is no effective mechanism to deal with transboundary flooding, she said.
To solve this, the government must seek collaboration with the neighbouring country to limit the impact of floods on people living downstream, she said.
It should also cooperate with countries along the lower part of the Mekong River to mitigate this risk as Thailand's Northeastern region is prone to floods, she added.
She said that huge volumes of water from Laos and water discharges from dams in China could cause flooding in Thailand's Northeastern region.
"The Mekong River Commission's mechanism doesn't work because it only focuses on data sharing. What we need now is a co-management system for Mekong River countries, including China," she said.
"People living along the Mekong River should have the right to stay safe from flooding caused by water discharged by the dams."
"If [Prime Minister Paetongtarn Shinawatra] deeply understands people's suffering, she should take immediate action to deal with the transboundary flooding by raising the issue for a regional discussion," she added.
"No one from the government has expressed a single care on the issue. This is a huge loss for the people."
The Thai Meteorological Department on its website warns that a monsoon is expected to strengthen on Tuesday across the country's Northeastern, Isaan and Central regions.
The monsoon will also cause heavy rain in Bangkok and the Eastern and Southern parts of the country, it said.
Tara Buakamsri, of Greenpeace Southeast Asia, meanwhile said deforestation is a key factor in the flooding disaster in Chiang Rai province.
He said Shan State in Myanmar, which is connected to Chiang Rai's Mae Sai district, is home to the headwaters the origins of the Mae Sai River and the Mae Kok River, which have overflowed and caused devastating floods.
Mr Tara cited data from satellite images taken from 2021–2023, which showed that over 3.1 million rai of forest land in Shan State had been changed into maize farms to serve feed mills.
Pianporn: Work with neighbours