For Nabin Lama, leaving Nepal after his annual home leave to return to his construction job in Saudi Arabia is not easy. What makes the journey bearable - even enjoyable - is the can of beer he can drink on the flight from Kathmandu.

As soon as the seatbelt sign dinged off on a flight to Mumbai - from where he and a couple of hundred other Nepalis would take a connecting flight to Jeddah - Lama rose to look for the stewardess.

"Beer," he bellowed, waving to her as she made her way down the aisle with a tray of fruit juice and water.

"It's a tough life there. But at least we can earn something and help our family," said Lama, 24, one hand on his passport, a white sticker across its green cover identifying a Nepali recruitment agency and his job.

"But we can't drink there. So we have a beer on the flight. It feels good," he said with a grin.

Lama comes from one of the world's poorest countries. On-going political instability since a decade-long civil conflict ended in 2006 has discouraged investment, hampered growth and curbed job creation in Nepal, forcing hundreds of thousands to migrate overseas for work.

Most go to the Middle East, Malaysia and India, from where they send remittances which make up almost 30 percent of Nepal's annual gross domestic product, according to the labour ministry.

Most migrants are in low-paid, unskilled jobs in construction, or work as security guards and domestic helpers.

Many face labour abuses including long hours, unsafe conditions and withholding of their wages and passports, say activists. Many are trafficked, tricked into doing jobs that they did not sign up for, or under conditions and wages far worse than they were promised.

Their families are not that much better off. Elderly parents, as well as young women and children left behind in remote villages are themselves vulnerable to traffickers and racketeers, and struggle with everyday hardship.

"There are hardly any young men left behind in some districts," said Nandita Baruah, deputy country representative at Asia Foundation, an international development organisation, in Kathmandu.

Families left behind may be duped into sending their children with traffickers posing as aid workers, or even selling their kidneys in India for money, she said.

"Migration is increasing the economic and social vulnerability of the country: people left behind are exposed to the harsh economic realities, and it makes them take greater risks, like trusting a trafficker or a kidney tout," she said.

More than 3.8 million permits to work abroad were issued in the decade to 2015, representing about 14 percent of the current population, according to Nepal's Labour Ministry.

This does not include the hundreds of thousands crossing the border into India, where they do not require a permit.