Titipong Khiewpaisal, the senior vice-president for marketing and sales at Advanced Info Service Plc (AIS), said mobile operators are promoting 3G services after rolling out nationwide network expansions.
Operators are working with smartphone makers to offer heavy discounts to customers who sign up for postpaid promotional tariff plans.
They are also stimulating their postpaid subscription bases by offering up to 50% discount for customers who want to shift to 3G postpaid services, Mr Titpong said.
He said AIS saw a sharp increase in the number of postpaid customers for the first time last year after facing no growth in the market for several years.
As of Dec 31, AIS's postpaid customers totalled 4 million, double the 2011 level.
Wichai Pornpratang, the vice-president for information technology and mobile communications at Thai Samsung Electronics Co, said 12-14 million smartphones could be sold in Thailand this year, equal to last year's figure, thanks to new innovative product models and 3G migration.
In addition, he said the fast pace of technological change in smartphones is expected to drive Thais to change their mobiles every 15 months compared with a rate of 18 months last year.
Mr Wichai said smartphones would account for half of the country's total mobile sales this year, up from only 20% in the past two years.
Smartphones with large screens of more than five inches and priced from 7,000 to 12,000 baht will enjoy the fastest growth.
To compete head on with its rival Apple's iPhone, Samsung yesterday released its new high-end smartphone here, the Galaxy S5. It retails at 23,800 baht in Thailand and will be introduced globally next Friday.
The Galaxy S5 features a 5.1-inch water-resistant screen, a 16-megapixel camera and a fingerprint scanner to protect the user's privacy.
Globally last year, Samsung sold 300 million smartphones, two-thirds of which were the Galaxy S series.