Members of the Pak Moon dam's Assembly of the Poor called on the Department of Water Resources yesterday to oppose Laos' proposed Don Sahong dam construction.
Assembly representatives met with Boonjong Jarusdumrongnit, the deputy director-general of the department, to plead for environmental protection and local community rights.
Krisakorn Silalak, the assembly's coordinator, said if the dam is built, it would have severe consequences for the fragile ecological system and fishing culture along the Mekong River.
"The Thai government must join local people in opposing the dam construction. It must protect and preserve traditional fishermen's way of life rather than focusing narrowly on economic growth," said Chanapa Khuendee, another coordinator with the assembly.
Residents are mainly concerned the dam will destroy the migration routes for Mekong fish, which would threaten the food supply of communities living along the river banks, Mr Krisakorn said.
"There are no measures or equipment that can help along fish migration if the dam blocks the passage," he said.
At the Pak Moon dam in Ubon Ratchathani's Khong Chiam district, fish ladders were built to allow fish to migrate downstream, but despite the ladders, fish numbers dwindled.
Residents cannot catch many fish there any more, he said.
Many locals had to abandon their nets and fishing jobs.
Mr Krisakorn suggested Thailand withdraw from being a member of the Mekong River Commission (MRC) if the Lao government continues to ignore the potential damage the Don Sahong dam would inflict on communities in neighbouring countries.
The Don Sahong is a proposed hydroelectric dam in the Siphandone area of southern Laos' Champasak province which will produce 260 megawatts of electricity.
It will block the main channel between Laos, Thailand and Cambodia that migrating fish pass through year round, Ms Chanapa said.
Mekong River communities in eight provinces — Chiang Rai, Loei, Nong Khai, Bung Kan, Nakhon Phanom, Amnat Charoen, Mukdahan and Ubon Ratchathani — will be affected.
Mr Boonjong said Thailand took a stand against the dam at a recent MRC meeting in Vientiane in February, when it demanded evidence of measures to counter the devastation a dam would inflict on the communities in the lower Mekong region.
"If the Lao government cannot assure us that it has effective measures, we will ask it to suspend the project until we are sure it can mitigate the impact," he said.
Meanwhile, countries in the MRC will hold a new round of meetings by the end of this year to decide their stance on the Don Sahong dam, said an official from the department, who declined to be named.