First off, visit voice.google.com and
get an invite.
Once you get your invite, you'll need:
1. A USA phone number.
2. A USA IP address.
3.
Gizmo account.
USA Number: You can use a friends number in USA, get your own Skype in or Gizmo number for $12. Or if you look even harder you maybe able to find a free DID number and answer it on your SIP device in Thailand.
USA IP: When you do the sign up, you'll need to working with your USA ip address. You can pay for this by getting a VPN, SOCKS proxy, SSL proxy or maybe even get lucky using
TOR.
During your sign up, you'll pick your number. As of now, i found several 5 repeat digit numbers like 420
222 2289 or 90
8 888 8807. You can search by number sequence or word to get that killer number.
Then Google will call the USA number you enter, and ask you for the 2 digit number on your screen. Once you pass this, you're in.
You can disable forwarding to this your USA number if it was just temporary.
Next you'll see one of the forwarding options is
Gizmo. Gizmo is a service like Skype, but they use the popular SIP protocol which you can use on a hard phone, soft phone or on your
SIP enabled Nokia.
Enter in your Gizmo SIP number, in Google Voice and you've forwarded your USA number to your Gizmo SIP number, which you can answer all kinds of places. Gizmo lets you forward calls to Skype, a mobile number or Asterisk.