Aflatoxins and aflatoxigenic fungi are hazardous to food security and safety since mycotoxins and related fungi in cereals significantly affect animal and human health. The relatively high frequency of aflatoxigenic Aspergilli isolates in corn samples remains a concern. Accordingly, we randomly collected corn samples from 10 farms in northern and central Thailand (TM1-TM10) and aimed to detect aflatoxigenic fungi using our recently developed methods: dichlorvos-ammonia (DV-AM) and whole-agar extraction methods. When we placed 100 grains from each sample on 20 agar dish cultures (five grains per dish) to monitor the emergence of fungal colonies, the presence of Aspergillus niger and A. flavus, with an emergence frequency of 1-8 and 1-7 per 100 grains, respectively, was detected. Some isolates of A. flavus produced aflatoxin B₁ and B₂ in the culture media, indicating typical features of aflatoxigenic A. flavus, whereas the non-aflatoxin-producing isolates produced kojic acid, thereby suggesting that they belong to Aspergillus section Flavi. Chemical analysis revealed aflatoxin B₁ and B₂ contamination in some grains and sporadic contamination with fumonisin B₁. Therefore, continuous monitoring and surveillance are required owing to the prevalence of mycotoxigenic fungi in corn.