Sangeeta Thapa founded Siddhartha Art Gallery in 1987 with eminent artist Shashikala Tiwari. She has curated over 500 shows of Nepali and international artists. She regularly gives consultations to collectors of Nepali art and initiates community art projects. She served on the Board of Patan Museum for six years and is a Fellow of the De Vos Institute of Arts Management. In 2009, she launched Nepal’s premier art event The Kathmandu International Arts Festival (KIAF) as a tri-annual event. In 2011, she established the Siddhartha Arts Foundation as a non-profit and organized the second edition of the Kathmandu International Arts Festival in 2012, through the Foundation.In 2016, Ms. Thapa co-curated the first exhibition of contemporary Nepali art at the Moesgaard Museum in Denmark.
In 2015, the Great Earthquakes struck Nepal causing a huge loss of lives and damage to homes and heritage sites. Taking this into account the third iteration of the Festival was postponed to 2017. In 2016, the Foundation decided to morph the Festival into a Triennale format and was recognized by the Biennale Foundation in Italy. The 2017 edition was curated by Philippe Van Cauteren from the S.M.A.K. Museum in Ghent, Belgium. The 2020 edition was also postponed due to the coronavirus pandemic and took place in March 2022. This edition is being led by the artistic director Cosmin Constinas from Para Site Hong Kong and two Nepali curators Sheelasha Rajbhandari and Hitman Gurung.
Ms. Thapa is the publisher of four volumes of poetry: Khulla Dhoka, Nirantar Khulla Dhoka, A Thousand Earths Thousand Skies, and Even the Moonlight can Burn. She has written a book on the drawings of Nepali artist Manuj Babu Mishra entitled In the Eye of the Storm and has written essays on contemporary Nepali art in the Gallerie Magazine (India) and for the Nepal Art Now exhibition catalog printed by the Welt Museum, Vienna. She has also contributed her essays to Telling a Tale, a publication of women's’ narratives, Nukta Art Magazine (Pakistan), and the VOW Magazine in Nepal. Ms. Thapa has been invited in the capacity of a speaker to Art Basel Hong Kong, New North-South Dialogue organized by the British Council and Manchester University in Sri Lanka, the Asian Curatorial Forum Dhaka, and to a panel on South Asian art organized by the Habiart Foundation, New Delhi.