You have to contact their support. I went through this change some time ago and all it took was one email. I was already prepared to send them all sorts of information and address proof documents but to my surprise, nothing was required
Choose a country first and afterwards and then make a call or write an e-mail to support. Or maybe you have already decided and need to find out if your desicion is correct?
if u living in India, Pakistan, Bangladesh, Malaysia, Indonesia, u can not change your adsense account country
Yep. In this case pretty much your only option is opening a new account via proxy and with different (think wife, mother, friend) details. Just make sure the person whose name you will use is actually trustworthy as they'll be getting cheques with your earnings