Vietnam is currently facing a significant DENV infection, with 320,000 cases reported in 2019, emphasizing the need for timely and accurate point-of-care diagnosis in the early stages. The loop-mediated isothermal amplification (LAMP) assay offers advantages as an alternative to traditional diagnostic methods. However, its false-positive results remain a concern. Therefore, this research aims to develop a LAMP assay with improved specificity for DENV-NS1 gene detection. Two LAMP primer sets named P4 and P6 for the NS1 region of the DENV-3 genome were designed. The assay was performed by mixing Dengue virus 3 (strain Philippines/H87/1956) DENV-NS1 ORF mammalian expression plasmid pCMV3-N-GFPSpark (positive control) and African Swine Fever Virus DNA (negative control) with nuclease-free water, isothermal amplification buffer, and either a P4 or P6 primer set. The mixtures were incubated at 65 ℃ for 45 min, and the results were confirmed by agarose gel electrophoresis. For assay enhancement, prehybridization-induced enhancement (PIE) strategy and organic additives (DMSO between 7.5% and 15%, betaine with concentrations of 0.4M and 1M) were adopted. Results show that the P6 set gave more differentiated positive results than P4 but was more prone to false-positive results. Further experiments with P6 were conducted to improve specificity. Experiments revealed that the PIE strategy did not significantly improve, while organic additives reduced false-positive results. The DMSO optimal concentration of 15% and a detection limit of 46 copies/µl were determined. Thus, the LAMP assay in this study was appropriate for dengue virus detection and could be further developed for point-of-care applications.