Thapa was in
New York for the
United Nations General Assembly during the
1960 coup d'état by
King Mahendra. He was arrested after landing in Kathmandu, but was taken to his residence. He met with Tulsi Giri and three days later had an audience with the king where he was asked to support the move. He came out in support of the move and planned the
Panchayat system along with
Tulsi Giri. On the insistence of Giri and Thapa all political parties were banned instead of the proposed ban on only Nepali Congress. He also coined the term
Panchayat for the
partyless political system. Thapa was made
home minister and minister for national guidance in the cabinet under the direct rule of King Mahendra. In April 1963, he was appointed the chairman of the
Rastriya Panchayat. He also headed the Commission for Administrative Power Decentralization that was formed in May 1963 which recommended the formation of panchayats at the village and district level. In July 1964 he was made home minister, panchayat minister and
deputy chairman of the
cabinet under
Tulsi Giri, but resigned in August. He resigned from the Rastriya Panchayat in July 1966. In 1967, Thapa was arrested for planning to issue a statement against the postponement of the Graduate's Organization elections. He was appointed the chairman of the central committee of the
Back to the Village national campaign in 1969. He campaigned in support of the multiparty side in the
1980 referendum on government reform. He rejoined
Nepali Congress in 1981, but left the party after Koirala's death in 1982. He was elected as the president of the Graduate's Organization in the
panchayat elections. == Rastriya Prajatantra Party (1991–2026) ==