Officials have said they are committed to amending the 16-year-old Trade Competition Act to ensure the changes are enforced within this government's tenure.
Santichai Santawanpas, deputy director-general of the Internal Trade Department, said authorities were preparing to hold a public hearing next Tuesday, with a focus on guidelines related to market domination.
"The guidelines are aimed at cutting business monopolies and promoting fairer competition," he said.
"They were passed earlier through the Trade Competition Board for approval, but certain parts of the private sector still felt unhappy. So a public hearing is needed to gather comments from all related parties before resubmission to the commission."
Once all parties, the commission and the cabinet are in agreement, the guidelines will be legally executed as an organic law of the Trade Competition Act.
Since the Act was passed in 1999, not a single successful prosecution has taken place. The only case to make it past the investigation stage involves complaints against the motorcycle distributor AP Honda of abusing its market dominance. The investigation took 10 years before the Trade Competition Board passed its findings to prosecutors in 2013. Prosecutors are still investigating.
Critics have said the current law is completely useless because it lacks a clear and workable definition of "market dominance".
The board, holding its first meeting under the incumbent government last October, agreed to improve the guidelines on market dominance.
It was proposed that a business entity would be regarded as dominating the market if it held a market share of more than 30% and had sales of more than 500 million baht in the preceding year.
Competition conditions would also take into account factors such as market structure, number of players, positioning, concentration, barriers to entry and access to manufacturing bases and distribution channels.
The Trade Competition Act currently defines market dominance as a market share in the previous year of at least 50% and annual sales of at least 1 billion baht.
Mr Santichai said the new guidelines would cut the market share to 30% as a measure of dominance but retain the annual sales figure of at least 1 billion baht.
He said the amendments had been fully supported by the National Legislative Assembly and other parties, which had agreed to ensure that they become law.
The amendments also would expand the scope of the law to cover state enterprises that run businesses in competition with the private sector, an upgrade of the Office of the Thai Trade Competition Commission to an independent body, and enhanced penalties and powers for that commission in filing lawsuits against violators.