Another option to avoid an overnight in DEL is LH through FRA. It gets in late enough that the wait for the morning flights to KTM are not too long.

However, I agree with most other posters here. Take the long way, and do a long layover in BKK.

The early morning flights from DEL to KTM are almost always delayed hours due to fog.

And yes, always sit on the right hand window.

Good luck in KTM - my parents' home country. Frequent power outages (on purpose - called "load shedding") - then again, hotels may have other means.