A train can drop you till Hasimara, 18km short of Phuentsholing. You may take a shared taxi to reach the border and spend the night there before getting your permits the next day. But make sure you have a confirmed hotel booking for Paro, P'ling and Thimphu.I am leaning towards Bhutan.
Since druk air is costing 40k return, I am planning more treacherous train + road journey. Can anyone guide about this route and days it will take from Delhi to to reach paro?