You can I have done it in the past from Europe and Asia. Though Asia time difference is a real killer. You can have real edge coming well prepared to first 30min.I would look at opening account for example with Interactive Brokers(I use them). You can deposit money in Euros, Dollars or Pounds and have the account base currency of your choice. If you are planning only US I would have base currency as dollars to avoid currency loans.If you really want to daytrade full time there are few things you need to know. US SEC regulation will require you to have minimum account balance of 25K$ and to avoid any issues I would advise to have at least 30K$ -35K$ for starters. Interactive Brokers also requires minimum of 10K$ to open an account, but if you deposit more this is not an issue anyway. They just want a proof identity and address (for example recent bank statement) and you have an account.Costs you need to calculate are comission, slippage and data. Your lot size is often small so you end up paying 1$ min commission for the trade per direction. If you trade major stocks slippage is not an issue in US. Data for stocks you end up spending anything between 10 - 30$ per month as amature for real time data. If you turn full time pro expect this to become at least 100 - 300$ per month.