Vietnam and Thailand are the two fastest-growing markets for smartphones in Southeast Asia in the first three quarters of this year, a report by GfK shows.

Both countries reported surges in smartphones sales and values from January to September in 2013 that are more than double those of the same period in 2012, GfK said in its report released Monday.

Vietnam posted a 156 percent surge in smartphone volume and 113 percent in value, while the respective figures for Thailand are 118 percent and 114 percent.

GfK tracked smartphone growth in the first three quarters of this year in seven Southeast Asian countries including Singapore, Malaysia, Thailand, Indonesia, Vietnam, Cambodia, and the Philippines, and concluded that intensifying demand propels smartphone sales volume by 61 percent.

Half of all handsets sold are now smartphones, and Android and bigger screen models are gaining popularity, the report shows.

In the first three quarters of this year, consumers from the above countries spent US$10.8 billion on nearly 41.5 million smartphones, according to the report.

Among the seven individual markets tracked, Indonesia has the greatest smartphone sales volume and value. Since the beginning of this year, Indonesian consumers have already bought 14.8 million smartphones worth over US$3.33 billion.

Thailand and Malaysia have the next highest smartphone sales volume with 7.2 million and 6.4 million units sold respectively.

However, in terms of smartphone sales revenue, the ranking of these two countries are topped by Malaysia, which garnered US$2.25 million while Thailand raked in USD1.96 million from January to September 2013.

“The increasing affordability of smartphones, particularly in developing markets, is helping many consumers in these countries make the switch from their basic feature phones to their very first smartphone,” highlighted Gerard Tan, Account Director for Digital Technology at GfK Asia.

“It is worth noting September as a significant milestone, as it is the month when sales penetration reached the halfway mark: when one in every two mobile handsets purchased in the region is now a smartphone.”

In terms of operating systems, the Android, with its 72 percent market share, continues to be increasingly sought after across six of the markets. This platform is most widespread in the Philippines, Malaysia, and Singapore, where the operating system now makes up 91, 83 and 81 percent of total smartphone sales in the countries respectively. In Indonesia, a proportion of Android smartphones sales jumped by 23 percent within a year, from 37 to the current 60 percent.

Larger screens are now increasingly prevalent in new smartphones.

Smartphones 4-inches wide or more occupied 13 percent of total sales last year, but now have more than doubled their share. In the first nine months of this year, one in four (27%) smartphones sold had a screen size of at least 4 inches.

“The latest trend in the market now is phablets, which are mobile devices with cellular voice functionality but a display between 5.6 inches and 6.99 inches,” said Tan.

“Launched only recently around mid-2013, over 460,000 have already been sold and we will likely see an increase as more models enter the market,” noted Tan.

“The substantial 50 percent of feature phone buyers in Southeast Asia who have yet to convert to smartphones presents much potential for manufacturers, and we predict a continued uptrend and exponential growth in the smartphone market in this region,” concluded Tan.