If your mother in the U.S. is more Lifetime Channel and QVC than CNN and NatGeo, the way she views your living in Cambodia is that you may have just as well joined the French Foreign Legion. It goes without saying you don't talk with her enough. This of course is not at all possible no matter what you do. Be that as it may, you owe it to her to make this crazy-making adventure of yours as easy for her to deal with as possible.
I have given up on Skype and calling cards as a way for my mother to reach me. Too complicated. “I forgot how to turn it on.” “Too many numbers.”
There is a better way. It's a little complicated but here goes.
First, get a phone number which is a local call for your mother. Never mind the Skype-in number because Skype won't ring on your smartphone in Cambodia unless you keep it running all the time and you'll be hit for the cost of calling Cambodia yourself at rates which are still a bit too high given the alternatives. I use the VOIP service called Localphone. The California number I use costs me a lousy $.99 per month (with an initial $3.99 set-up charge).
The problem with Localphone, like other similar VOIP services, is that although they have a mobile app, you can't use it to make or receive calls in Cambodia directly. But, you can do both, with some work, if you use Localphone's internet phone feature. This requires that you route calls through a SIP softphone provider compatible with Localphone. If you're an iPhone or Android mobile user, the best service I've found which fits the bill is Bria. You'll find instructions on how to set up your Localphone account to route through Bria on the Localphone website.
Once set up properly, when a caller dials your Localphone number the Bria mobile app will ring your Cambodia phone. Call quality is excellent and the received call is free. Making calls out could not be easier, the Bria app interfaces seamlessly with your iPhone/Android contact list. Bria is always there on your phone but it runs as a background service rather than a application and thus uses little battery or memory. It just works. Bria will cost you $7.99 at the app store. That's expensive for a mobile app but it's an extremely full featured application with terrific support.
There's one more thing you can do. The above gets you the ability to make and receive calls to and from Mom, but without a voicemail function. For this you want Google Voice. To sign up with Google Voice from Cambodia you'll need to use a US proxy server to fool Google into thinking you're in the U.S. Tunnelbear is a proxy server that has worked for me but there are lots of others you can try for free. Unless you already have a US cell provider, you'll need to use your U.S. Localphone number to register with Google Voice, which number they will ring to verify your worthiness to enter into the Google Voice club.
Once you're into Google Voice you can tell Google Voice to forward calls to your Localphone number. So now instead of calling the Localphone number Mom will call the Google Voice number, which will be forwarded to the Localphone number which Bria will ring on your mobile. If you don't pick up, the call will be sent to Google Voice voicemail. You'll receive a notification on your mobile that the voicemail is waiting for you, as well as an often whacky transcription of the recorded voicemail. Call her back using your Google Voice number (using Click to Call) and the call is free. If your Mom is not in the U.S. you’ll pay for the call at the applicable Google Voice rate for the destination country.
It sounds like this would be messy but in practice it's not. The three components work fine together with good call quality and no delays, and most importantly, it's an easy local call for your Mom that she knows will reach you immediately.
So no excuses, if your mother is not among the technically savvy, be a mensch and make it easy for her to reach you. It can be done.