The telecom regulator will ease the rules for True Move and Digital Phone Co (DPC) and let them offload their existing mobile data traffic to the 1800-megahertz spectrum for one year to alleviate congestion.
Mobile operators, especially leader Advanced Info Service (AIS), are faced with the possibility of massive traffic jams as the rise of affordable smartphones and tablets fuels a surge in mobile data consumption.
"Operators can also temporarily use the 1800-MHz spectrum to provide 3G and 4G wireless broadband service until July next year to ease data traffic congestion and relieve poor signal quality," said Takorn Tantasit, secretary-general of the National Broadcasting and Telecommunications Commission (NBTC).
The 1800-MHz spectrum, previously used by True Move and DPC, a unit of AIS, was originally tabbed for an auction to provide 4G service next month.
But the military regime ordered the NBTC to suspend the 4G spectrum auction for one year and to amend several impractical sections of the Frequency Allocation Act before any bidding takes place.
True Move and DPC were told by the NBTC to retain their remaining 2G customers on the 1800-MHz spectrum for one more year after their concessions with CAT Telecom expired last Sept 15.
The regulator has given both operators an additional year to speed up transfer of existing 2G customers to other networks, but they are not allowed to acquire new subscribers.
True Move has just over 5 million customers on the 1800-MHz spectrum, down from 17 million last October. DPC has 4,000 users, down from 74,000 last year.
Mr Takorn said both operators must provide a strong mobile signal to existing 2G users in compliance with customer retention requirements.
Mobile operators can also arrange their traffic on all existing frequencies and transfer some of the traffic to the 1800-MHz spectrum under network roaming agreements.
Service revenue from traffic transfers to the 1800-MHz band will be subject to concession fees of roughly 30% of total revenue, instead of the licensing system's 5%.
An industry source said AIS stands to benefit most from the relaxed rules because the operator is suffering from heavy traffic congestion. The country's biggest mobile operator will have the least amount of bandwidth when its 2G concession with TOT Plc expires in September 2015.
AIS operates 2G service on 17.5 MHz of the 900-MHz spectrum. It has 42 million subscribers, 26.5 million of whom are 3G customers.
In comparison, second-ranked DTAC boasts the most bandwidth with 50 MHz of the 1800-MHz spectrum. Its concession with CAT Telecom expires in 2018.
Third-ranked True Move, through its subsidiaries Real Move and Real Future, offers 3G on 15 MHz of the 850-MHz spectrum with concession owner CAT Telecom.
In addition, the big three mobile operators each provide 3G service on 15 MHz of the 2100-MHz spectrum.