The House of Representatives rejected a proposal to establish a special committee to further study the Land Bridge megaproject, with government MPs arguing that multiple reviews had already been conducted and additional scrutiny would duplicate existing work.
MPs on Friday voted 266 to 174 against setting up the committee after hours of debate over the proposed transport corridor linking the Gulf of Thailand and the Andaman Sea under the Southern Economic Corridor (SEC) scheme.
Supporters of the project, led largely by the Bhumjaithai Party, argued that the government had already commissioned several studies examining its economic, environmental and social impacts.
Ranong MP Kongkrit Chatmalirat of Bhumjaithai said the project represented a long-awaited opportunity to improve southern infrastructure and strengthen international freight transport links between the Andaman coast and the Gulf of Thailand.
He acknowledged concerns among local communities over environmental impacts, fisheries, tourism and livelihoods in Ranong and Chumphon, but said those issues could be addressed through preventive measures and compensation schemes.
Mr Kongkrit said parliament and the government had already undertaken extensive studies of the project.
"In previous parliamentary sessions, committees were established to study this issue," he said. "The findings, including support and opposition from local communities, were submitted to the cabinet on Feb 15."
He added that Prime Minister Anutin Charnvirakul had established another committees, chaired by the deputy prime minister and finance minister, along with three subcommittees, to continue examining implementation plans and public consultations.
"The government has already set up several committees to study the Land Bridge project. There is no need to establish another one," Mr Kongkrit said.
Opposition MPs warned against proceeding without broader parliamentary oversight, citing concerns over economic risks, land speculation and national security.
Democrat Party leader Abhisit Vejjajiva described the project as a "misconception", arguing that local communities would receive limited benefits while contractors and land speculators stood to gain the most.
He warned the project could become "a monument" to policy failure if shipping demand failed to materialise. He also cautioned that turning southern Thailand into a strategic transport hub could expose the country to rivalry among major powers.
People's Party leader Natthaphong Ruengpanyawut said southern development should instead focus on agriculture, bio-economy industries and public services such as clean water, education and healthcare.
Prachachat Party leader Pol Col Tawee Sodsong questioned discrepancies between separate feasibility studies conducted by Chulalongkorn University and the Office of Transport and Traffic Policy and Planning, citing sharply different projections for project costs and returns.
Transport Minister Phiphat Ratchakitprakarn defended the scheme as a long-term economic strategy.
"It is a major opportunity that Thailand should pursue," he said.
