During, Panchyat regime(70s and 80s and even 90s), There were a bunch of countries that did not required visa for Nepalese travellers. Reason was nepalese economic stading int he world economy was pretty good, people who went abroad always returned back, they was not a big influx of nepalese going abroad like today. 

At present, Only singapore does not require visa for nepalese travelers. Also, this holds true for india, well india-nepal has an open border agreement. 

Countries that did not required visa for nepalese travellers in the past were Hong Kong, Germany, Japan, Thailand, Burma(myanmar)..etc