The provisions in the new constitution of Nepal indicates that non-residents have the right to engage in the economic and social affairs of their country of origin, but will not be allowed to engage in politics, vote for their representatives or be elected.
It is not easy to have an accurate figures regarding Nepalis living abroad as there is a large population of migrant workers in India who don’t stay in one place, and there are tens of thousands of Nepalis staying illegally in east Asia and Europe. Besides, there are up to 200,000 internally displaced within the country who would also need to vote. In 2006, more than 10 percent of Nepalis lived outside of the country.
Before 2013 Constituent Election, the Election Commission of Nepal’s commitment to ensuring voting rights for Nepali citizens living abroad was cancelled. The EC lacks the authority to promulgate election laws, while the leader failed to take major parties and the government into confidence and convince them of the necessity of electoral reforms.
Source
http://nepalitimes.com/news.php?id=12165#.V337-ryO5E4
http://www.nepalelectionchannel.org/english/expert-view/836-ad-hoc-elections.html
http://www.asianews.it/news-en/Non-resident-Nepalis-complain-that-the-new-Constitution-deprives-them-of-voting-rights-34859.html