You will need to file form 1040NR. $01k distributions are taxable, so if you take out more than the personal exemption you will owe income tax in addition to the penalty (so if you do not need the money urgently, I would suggest to withdraw it over sever years and keep the distributions in the amount of the personal exemption) . Also make sure to provide the 401k custodian form W8BEN before you make any distributions
