The NBTC's superboard has urged the Office of the National Broadcasting and Telecommunications Commission to delay the planned auctions of the fourth-generation (4G) spectrum if the regulator cannot find a greater amount of frequency for sale.
Meanwhile, the head of the country's third-largest mobile operator, True Move, also wants the government to bring the unused 2600- and 2300-megahertz spectra into the auction together with the planned 4G spectrum auctions this year.
The high-band frequency is needed to ensure operators deliver highly efficient, low-cost 4G wireless broadband service, True Move chief executive Suphachai Chearavanont said.
"The auction of only two slots or 12.5 MHz each of the 1800-MHz spectrum [scheduled to take place on Nov 11] will not be enough to provide efficient 4G service," said Gen Boonyavat Kruahongs, chairman of the NBTC's superboard.
Mr Suphachai said: "At least 20 MHz of bandwidth is required to provide 4G service efficiently."
Gen Boonyavat suggested at least 20 MHz of bandwidth per licence was needed for practical 4G service.
The proposal to delay the 4G spectrum auctions is part of the superboard's annual performance and evaluation report.
"If there is a further delay of a few months in order to allow the NBTC to bring additional frequencies for auction, it could be a better way for the overall industry in the long term," Gen Boonyavat said.
He said the NBTC could reclaim the unused spectra from second-ranked operator DTAC, for instance, in order to bring it into auction together with the 1800-MHz spectrum.
Total Access Communication Plc (DTAC) recently proposed returning its unused 25 MHz band on the 1800-MHz spectrum to the NBTC for the 4G auctions, with no requirement for compensation despite DTAC's concession with CAT Telecom not expiring until 2018.
Mr Suphachai said there was 120 MHz of bandwidth on the 2600-MHz spectrum, more than sufficient for mobile operators to deliver high quality 4G service.
He also opposed claims that the 2600-MHz spectrum was not an internationally recognised standard and would not be practical for 4G service as very few handsets were based on this spectrum.
"If the spectrum is not an international standard with very few handsets available, then why do neighbouring countries such as Singapore, Hong Kong, Malaysia and the Philippines use it for 4G commercial service?" Mr Suphachai said.
He agreed with DTAC's proposal to return its unused spectrum for the 4G auctions.
However, he said it would be a complicated process and doubted CAT would be amenable to the proposal, as the state telecom would risk falling under Section 157 of the Criminal Code for negligence of duty.