The National Broadcasting and Telecommunications Commission (NBTC) plans to allow the winners of its 4G mobile auction on the 1800-megahertz frequency to run 2G mobile services on networks whose concessions are set to expire this year.
The regulator has scheduled an auction for 25-MHz slots of the 1800-MHz frequency by September next year, after True Move and Digital Phone Co (DPC) return their spectrum to the NBTC once their concessions expire in September.
Jesada Sivaraks, secretary to the NBTC's vice-chairman, said the watchdog is asking the second-ranked mobile operator DTAC to return its unused 25 MHz in the 1800-MHz band in order to auction it simultaneously with those of True Move and DPC.
But the NBTC has no authority to force DTAC to return the frequency, as its concession will expire in five years.
DTAC owns 50 MHz of the spectrum, but the company runs only 25 MHz under a concession with CAT Telecom due to expire in 2018.
"If we could obtain the unused 25 MHz from DTAC, it would give us much more flexibility to reallocate the spectrum slot in order to better handle existing 2G users after the concessions end," said Mr Jesada.
He said the planned 4G auction may offer two licences, consisting of 15 MHz of bandwidth each. The winners could obtain an additional 10 MHz each for providing 2G services.
The winners would be allowed to gradually migrate their customers from 2G to 4G in the long run.
True Move and DPC have a combined 18 million customers using 2G services.
At least 10 million customers would still use the services after concessions expire, said Mr Jesada.
The NBTC's telecom committee set up a subcommittee in March to oversee the reallocation of the 1800-MHz frequency. It is responsible for drafting an information memo on the 1800-MHz band, evaluating the spectrum value and setting a reserve price for spectrum slots.