Lord Buddha was born in Nepal. His birthplace at Lumbini is a major pilgrimage site for people around the world. Yet in spite of its popularity, there is not a direct luxury tourist bus to Lumbini.
The best option is to take a private vehicle to Lumbini. A private car is not only more comfortable than bus service, but it is also faster and direct. Local buses have crowded seating with little legroom. The cost is quite reasonable and much more comfortable.
If you desire, you can alternate go to the Indian border with the same private car at Sunauli. Be wise. Arrive relaxed and in a peaceful frame of mind by taking a private vehicle to Lumbini approx 300 km. The departing time is flexible and informs us what time would you like to depart from Kathmandu.