Secretary-general of the National Broadcasting and Telecommunications Commission (NBTC) Takorn Tantasit said the regulator's five-member telecom committee is likely to ask the court to withdraw the case.
Mr Takorn's comments came as media organisations came out in unison to criticise the committee's action, describing it as a threat to academic and media freedoms.
Thailand Development Research Institute (TDRI) researcher Duenden Nikomborirak told Thai PBS reporter Nattha Komolvadhin during an interview last week that the committee's decision could cause the country 160 billion baht in opportunity cost.
The interview led to the committee to sue both the academic and the interviewer for libel.
Ms Duenden was referring to TDRI's research paper on CAT Telecom's 1800MHz mobile phone concessions to 2G mobile phone operators True Move and Digital Phone, which are due to expire on Sept 15 this year.
Instead of requiring the two private firms to return the frequencies immediately to the NBTC for 4G mobile phone licence auction, the panel has decided to give them one more year to return the spectrum to the regulator.
The one-year delay will push back the 4G auction.
The panel cited the possible impact on the firms' 17 million customers who are still using the 2G mobile phone service, which is operated on the 1800MHz spectrum, as the reason for the extension.
Thai Broadcast Journalists Association president Visut Komwatcharapong said the legal move by the telecom regulator came as a big surprise.
Ms Duenden said she had offered her opinions to Thai PBS from an academic perspective and had no bias against the telecom committee.
As a scholar, she said she was ready to accept any criticism and debate on the impact of the delay.
The telecom committee has yet to clarify the valuation of 4G utilisation, which will be damaged by the delay of the auction, she said.
TDRI chairman Somkiat Tangkitvanich said the legal move also surprised him because the return of the 1800MHz frequency is a public issue that has to be commented on and scrutinised by academics in the interests of the public.
The committee's lawsuit against one of its academics was the first in the TDRI's 30-year history, he said.
Mr Somkiat said that while the NBTC's telecom committee claims the postponement is aimed to protect 17 million customers for another year during the transition period, it has never come up with an estimate of how much the country would lose as a result of the delay in the 4G licence auction.
Pradit Ruangdit, president of the Thai Journalists Association, said three media associations are ready to provide assistance to Ms Duenden and Natta.