I'm in the UK at the moment. I have a friend who lives in Chiang Mai with who I regularly exchange SMS messages. For the past couple of months he's been unable to receive any SMS that I send to him. He can send them to me successfully. We can both call each other successfully. He just can't receive MY SMS. He hasn't changed his SIM or his phone.

Anyone suggest a reason why this might be happening?

Have you tested your ability to send SMS?

Try sending an SMS to someone else...

• in the UK on the same network
• in the UK on a different network
• in Thailand using AIS / DTAC / True or TrueH (try one of each)

this will let you know if any of your SMS are making it out,

While it's easy for a mobile network to deliver sms to their own clients, an sms being sent to another network (never mind another country) requires an sms gateway and open exchange agreements that don't always work both ways and things are always changing.

Let us know how you make out with the tests.

I can send SMS to anyone in the UK. I can send them to other folks in Thailand. I can even send them to my self. I have a 2 sim phone using 2 different carriers. I can do all of these things using both of the sims on my phone.

OK, if it works to send sms to folks in Thailand who are on the same network as your friend, and they still receive them after your friend stopped receiving them -- this would eliminate the issue being on your side.

So, the sms are either being specifically blocked by your friend's mobile network or by a block feature on his phone.

Do you know the the make/model of his phone?

It's a very old 2G Samsung. I don't know the model number.