DTAC operates 2G mobile service on the 1800-MHz band under a concession with CAT Telecom, which is due to expire in 2018. The company also runs 3G HSPA on the 850-MHz spectrum under agreements with CAT.
It has 25 million subscribers, while Advanced Info Service has 34 million and True Move 20 million.
Mr Pakorn said availability of 2100-MHz-enabled handsets will be crucial to attract mobile users to 3G.
"As many as 50 million handsets in Thailand must be replaced once the 2100-MHz 3G service is launched," he said.