If one has existing stock account, could it be possible to trade stock using ETrade, Scotrade while in Nepal?

If you mean, can you operate an existing US-brokerage account from Nepal, then yes you should be able to (you may face the "we-didn't-recognize-this-computer-please-enter-your-pet's-name" type of questions). I can confirm it works for E*Trade and Fidelity.

Good luck!

vivant
that's what exactly i was willing to understand.
thank you dude.