A round trip from Pokhara to Lumbini Kathmandu is always an excellent option for a round trip through southern Nepal. You have multiple options to get there. It is up to you. What kinds of transportation do you opt for it? The road is about 200KM, and the public bus takes about 7hrs drive to get there. At the same time, you have options for domestic flights from Pokhara and also private cars.
Flights leave every day at 8:30 AM by Buddha Air, and local buses have multiple departures though recommended to get an earlier bus always, and the private car leaves on your time and interest.
The public bus is the cheapest option, and a private car and flight are almost similar in cost the US $100, but the private car is a little more expensive than the flight. A taxicab is more relaxing, and options to visit several places along the trail. We drive to Lumbini via Syangja, Tansen Palpa.
In between the Pokhara and Lumbini, there is Chitwan National Park, famous for Jungle safari and Tharu culture. It is 143KM far from Pokhara, and Lumbini to Chitwan is about 153KM. We can arrive at Chitwan by a domestic flight from Pokhara and Kathmandu.