The police detained the duo, who were travelling to Bangkok after acquiring Nepalese passports by producing fake citizenship certificates, Kathmandu Metropolitan Police Circle said.
The persons arrested were identified as Lobsang Jamang and Keasalg Rinjen.
The police had stopped them at the airport just before they were to board the Thai Airways aircraft.
The security personnel had interrogated them after finding that they could not speak Nepali language, the police added.