Junker has good information that refers to when Nepal became republic.
If want to worry/plan well ahead, contact the airline if you are flying in and they can guarantee a good source of choices. Obviously, some early planning and going through a consulate or embassy is the safest way to remove advance fears.
All of the airlines flying into Nepal will have a means to get a visa ahead of time and avoid problems if you arrive late or if it happens to be a local holiday. Local or government holidays can be a real obstruction for delays in every country.
There are several international airlines that service the short strip there and an arrival from Bangkok should not be a problem, just as if you are on Air India. - Before my temporary KLM short term detention outside of passport control at the airport, a visa was not needed. I arrived a year later by road from India and did not need a visa (borders are quite loose everywhere, especially for some types). When I got to a hotel in Kathmandu, they arranged for a visa upon registration at the normal cost with no problem.
It costs a little more to do things in advance and provide for all eventualities, but that is not always possible. If you have some good identification and last minute problem can be more inconvenient and costly.