How to integrate mobile SIM cards into your business VoIP system in Thailand



Modern VoIP solutions offer fantastic mobility for your telephony because you can take your DID number and extension anywhere with an internet connection. However, many businesses and employees in Thailand still prefer to use mobile numbers.

This is because of the familiarity and habit of sharing mobile numbers and communicating by mobile phone, but there is some anecdotal evidence that many people ignore incoming landline number calls more than mobile numbers.

Whatever the reasons, a lot of Thailand-based businesses considering a VoIP solution ask how to integrate mobile SIM cards into their business telephony, instead of letting employees use their private mobile numbers. Regrettably until now, this has been impossible as Thai law prevents mobile numbers to convert to internet protocol.

There is a now a practical workaround to this dilemma, in the form of a Closed User Group (CUG). In this CUG, mobile numbers are added to your group of DID numbers and extensions, and therefore become part of the same telephone eco-system.


So what are the benefits?



  • Within the CUG, all calls are free of charge, which means your staff in the field on their mobile phones can call their colleagues in the office (and vice versa) for as long as they like, and it doesn’t cost a cent…just as if they called from extension to extension.
  • Calls from customers to the office can easily be transferred to a CUG mobile number, or can be included in a ring group or follow-me routing.
  • SIM cards and numbers are owned and assigned to employees by the company; if and when an employee leaves the company, customers calling their contact still call the company number instead of the employee who has moved on
  • All SIM card voice and data billing is neatly charged directly to the company instead of involving complex staff expenses claims.


Currently this solution still has some caveats:


  • Transfers from mobile to other CUG mobiles or extensions are not possible
  • Many standard VoIP features don’t apply to mobile SIM calls, for example call recordings, call history, voicemail to email, etc.…
  • SIM cards and voice & data service are provided and billed separately by a telco, at different rates to your VoIP internet rates.


However, for those companies in Thailand that are using or considering a VoIP system, and require the integration of mobile SIM numbers for their staff, the solution describes above works great and offers good business value, especially for companies with sales agents.

For more information, contact us on +66 2 105 4068 or email This email address is being protected from spambots. You need JavaScript enabled to view it. .