 This research investigated the properties of coconut fiber, CF, reinforced lateritic soil, LS, mixed with municipal solid waste incineration fly ash, MSW-IFA, based geopolymer as a green construction material, and found that an LS-MSW-IFA ratio of 101, an Na2-CY03 or NaOH ratio of 80-20ths, an NaOH concentration of 5 molar, and a CF content of 0.5% meet the 7-day UCS requirement for non-bearing masonry units, and offer the highest FS. The addition of CF promotes geopolymerization reaction, and results in a denser matrix compared to the sample without CF. This article was authored by Wizardzak Tapyong, Chertzak Cixiopatinapong, Natya Wonglacorn, and others.