I am now live in Yangon,Myanmar and can not use my debit Visa card for payment of App Store.

The iTunes Store in a country is intended for use only by that country's residents, and only while they are in the country. To use the iTunes Store in a country you need a credit card (or other card type if acceptable in a country) issued in that country, billed to an address in that country, and also be physically present in that country when using the store. You are also restricted to waiting 90 days between country changes.

E.g., "The iTunes Service is available to you only in the United States, its territories, and possessions. You agree not to use or attempt to use the iTunes Service from outside these locations. Apple may use technologies to verify your compliance." - http://www.apple.com/legal/itunes/us/terms.html#SERVICE

You must use a payment method with a billing address, and use the Stores, in the country in which you reside.

Payment methods that you can use in the iTunes Store, App Store, and iBooks Store - Apple Support

Change or remove your Apple ID payment information - Apple Support

Sorry, but if you do not live in the U.S, then you cannot use the U.S iTunes store.