Banthoon Lamsam was born on 15 January 1953, a son of Bancha Lamsam and Thanphuying Sam-angwan Lamsam (maiden name Mom Rajawongse Sam-angwan Devakula; daughter of Prince Priditheppong Devakula and Mom Rajawongse Sa-ang Pramoj). Bantoon has two younger sisters. Bantoon is a grandson of Choti Lamsam who founded Kasikornbank in 1945 as Thai Farmers Bank. Banthoon graduated from Saint Gabriel's College and Srinakharinwirot University Prasarnmit Demonstration School. He studied at Phillips Exeter Academy from 1967 to 1971[5] before going on to earn a bachelor's degree in chemical engineering from Princeton University and a masters of business administration (MBA) from Harvard Business School (HBS).[4]