A survey by the Electronic Transactions Development Agency (ETDA), which is under the Information and Communication Technology (ICT) Ministry, found that internet usage among Thais increased sharply to 50.4 hours a week this year, compared with 32.3 hours a week or 4.6 hours a day in 2013.
The survey was conducted in April and May and involved 16,600 respondents, said EDTA director Surangkana Wayuparb.
It also found that transgendered people spend a longer on the internet with an average of 62.1 hours per week.
Ms Surangkana attributed the longer internet usage time to the greater availability of affordable smartphones and wireless broadband internet coverage and free public WiFi.
Accessing the internet via smartphones while on the move also increased sharply to 6.6 hours a day.
Around 8.4% of respondents use internet-connected smart televisions after 8pm, spending an average 3.4 hours a day.
The top three internet activities on mobile phones are chatting via social networks, catching up on news and searching for information.
The primary use of the mobile internet was for entertainment and communication purposes. Users access the internet via desktop computers mainly to seek information.
Ms Surangkana also said that 38.8% of respondents use mobile phones for online shopping and 29.9% use the devices for mobile banking.
The ETDA also conducted a survey about risky online behaviour. The survey found that teenagers often share personal information including their name, check-in location, photographs and mobile phone number with strangers. "Such behaviour poses privacy risks,'' Ms Surangkana said.
Other high-risk behaviour associated with mobile internet usage are users failing to install antivirus and security software and not setting up personal passwords.