Thapa, who holds the Foreign portfolio as well, said the landlocked Himalayan country has entered a new phase of economic development after promulgation of the Constitution.
He also underlined the importance of democracy whose absence, he said, fuels rebellion.
Thapa, who had accompanied Nepal Prime Minister K P Oli during a visit to India last month, identified democracy, free market and culture as the "three pillars" of peace.
Speaking on the occasion, Pakistan's former Minister
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Sherry Rehman said her country was fighting one of the "largest inland wars" against terrorism and doing it "alone".
Rehman also highlighted the refugee crisis, including in Pakistan, saying that such inequality will incubate fear, conflict and add to the vector of economic and social conflagration.
Rehman was speaking in place of former Pakistani Prime Minister Yusaf Raza Gilani, who could not make it to the event.
Apart from Thapa and Rehman, the other speakers who spoke on the topic 'Creating a Peaceful World of Tomorrow' include former Bhutanese Prime Minister Jigme Yoser Thinley and former French Prime Minister Dominique de Villepin.
Without taking names, Thinley denounced the exchanges of military threat among nuclear-powered nations which, he said, amounted to "insanity". Focus on "wrong goals" is propelling the society in the direction of a "catastrophe", he said.