The Peace and Order Maintaining Command would find it nearly impossible to block provocative political comments on the web, local internet providers say.
The POMC has demanded political activists be silenced, but it says internet users can resort to other website hosting services overseas to post their comments.
By Tuesday the National Broadcasting and Telecommunications Commission (NBTC) and the army had shut down 2,000 unlicensed community radio stations plus 1,000 licensed stations.
The army also ordered at least 11 cable and satellite TV stations to stop broadcasting, pending further notice.
Legal and technology experts said the POMC could use web filtering or blocking techniques to prohibit the use of websites to disseminate provocative political comments.
Wanchai Vach-shewadumrong, deputy managing director of Internet Thailand, said websites or content providers that use web hosting servers outside Thailand cannot be blocked.
Local ISPs have no authority to gain access to their sites, especially global media networks such as Facebook and YouTube.
"Local international internet gateway providers can only ask for cooperation from regional telecom operators such as those in Singapore to ban the targeted websites," he said.
Prinya Hom-anek, founder of ACIS Professional, a local leading information security training centre, said video sharing would emerge as a key media communication channel for political activists now that satellite TV and community radio stations are prohibited from broadcasting.
The army might need to set up a special working team to track down any blacklisted websites, he said.
Paiboon Amonpinyokeat, founder of P&P Law Firm Co, said the army under martial law has the authority to ask ISPs to remove targeted content from the sites including Google's YouTube video archive, however difficult it might be to achieve.
Apisilp Trunganont, product manager of Internet Marketing Co, who oversees Pantip.com — the largest local webboard with 2.5 million visitors daily — said the company's website is cooperating with the military and is monitoring comments posted on the political "Rajdumnern forum" in particular.
The NBTC admitted it is difficult to block provocative information posted on video-sharing sites such as YouTube or Facebook because their servers are overseas.
The NBTC and the POMC yesterday asked 105 representatives from 51 internet service providers to help filter news and comments that intentionally "distort facts, instigate disorder, or create fear and misunderstanding''.
NBTC secretary-general Takorn Tantasit said ISPs, as the licensees of the NBTC, are being urged to monitor content on their websites and issue warnings to their content providers in cases where material is found which might fit the army's description.
Mr Takorn said the NBTC has asked ISPs to block websites that post provocative content within one hour. True Corporation closed six websites yesterday in line with the martial law announcements.