Abstract Coral reefs are one of the most biodiverse marine ecosystems. Diverse microbes are associated with corals, including zooxanthellae, protists, prokaryotes, and viruses. This study aimed to investigate the genetic diversity of the culturable fungi associated with scleractinian corals in the Gulf of Thailand. Ribosomal DNA sequence analysis and morphological analysis of 130 fungal isolates revealed a high diversity of fungal phylotypes from three coral species: Pavona decussata, Pocillopora damicornis and Porites lutea. Ascomycota was the most abundant fungal phylum. The predominant orders included Eurotiales, Cladosporiales, Hypocreales, Mycosphaerellales, and Diaporthales. There were eight orders of the Basidiomycota dominated by Polyporales, Hymenochaetales, Agaricales, and Wallemiales. A principal component analysis was performed to compare abundance and correlation between the fungal communities, sampling locations and coral species. The results showed that the dissimilarity of fungal communities corresponded to geographic localities. On the other hand, there was a considerable overlap between the fungal communities of different coral species. The results from this research provide information on the diversity and ecology of the fungal communities associated with scleractinian corals in the Gulf of Thailand.