The National Broadcasting and Telecommunications Commission (NBTC) pointed out that the second-ranked mobile operator instead needs to ask permission to do so from its concession owner CAT Telecom.
DTAC has raised two options to provide 4G. One is for the NBTC to let DTAC provide 4G service on its unused portion of the 1800-megahertz frequency under a 2G concession with CAT Telecom.
The alternative is to return the unused 25 MHz of mobile spectrum to the NBTC for auction. DTAC has 50 MHz of the 1800-MHz spectrum under a concession with CAT due to expire in 2018.
Col Settapong Malisuwan, an NBTC vice-chairman, said the request by DTAC must be passed on directly to CAT, which could negotiate on apossible amendment of the 2G mobile concession contract to allow DTAC to do so.
"We have no authority to intervene in this matter," he said.
Col Settapong said DTAC could face legal action if it moves ahead with its 4G plan without CAT's approval.
He also asked why DTAC does not operate 4G service on its existing 2100-MHz network, similar to True Corporation.
Amending the existing concession is a difficult task for DTAC, said Col Settapong.
CAT chief executive Kittisak Sriprasert was not available for comment Tuesday.
DTAC chief executive Jon Eddy Abdullah has insisted his company can run 4G service under the existing 2G concession, saying that mobile operators were earlier allowed to upgrade their 2G networks to 3G using high-speed packet access technology.
The company also reiterated it will not return unused spectra to CAT for the state agency's own service as ordered by the information and communication technology minister.
In another development, the NBTC's telecom committee Tuesday came up with a resolution to ask SCB Asset Management, which handles True Corporation's infrastructure fund, to apply for a type-3 telecom licence to operate the fund.
NBTC vice secretary-general Korkij Danchaivichit said the resolution is to comply with Section 7 of the Telecommunications Business Act.
SCB Asset Management last month asked the NBTC to clarify whether the company needs to apply for a licence before operating the infrastructure fund for True Corporation.