I was in States for 10 years and went back applied for Visa again for PHD. They handed me like piece of cake even though I didn't have any assistantship or fellowship. However they asked me how you going to support yourself w/o funding. I told them my assistantship is pending. I should be ale to get it for next semester . They gave me and my spouse the visa. It was back in 2012. Hope it helps. Documents I provided were: PHD acceptance letter, transkript of first semester, (finished a semester before going to Nepal) , previous degrees from the US university, i20 for me and spouse, marriage certificate, photos, and other stuffs like bank , property etc. questions asked: oh you were in States for Long time, what you studying, how you were going to support your study? Etc. he asked my spouse , ever been outside of the country, first passport? where the marriage took place? I crossed question him while he was checking my documents , where you from in States, he said California, I told him beautiful weather ? He smiled . ;)

@tesko_baje: Thanks for those encouraging words.

@Kaalubaby: Really appreciate you taking your time and providing detailed response. Did you get married when you returned back to Nepal or were you already married before returning to Nepal (during 1st semester of PHD).

US embassy in Nepal is a joke. I challenge everyone who think it's not a joke or scam. It doesn't matter what's your background is your chances of getting visa in US embassy in Nepal is always 50/50 which means it's complete random process.
I once gave an example of random number generator as US embassy consular in Nepal.