Geographic information systems (GIS) have played an increasing role in spatial analysis of linguistic data, especially in geolinguistics and regional dialectology. In this study we collected lexical data on the Chiang Mai dialect from 500 informants and examined different variants of the words they used. Data points were interpolated using an ordinary kriging approach and an estimated surface of each variant was created from these sample points. The resulting surface was overlaid onto a topographic relief map and displayed in three dimensions to facilitate the exploration of spatial patterns between physical and social variables. Whereas many language atlases traditionally present dialect observations using point symbol maps, a 3-D interpolated map has proved to be a useful tool for visualizing cooccurrences of multiple variants of the same word at the same geographic location. This technique also allows linguists to examine a general trend of dialect variation in Chiang Mai, which might not be revealed on a two-dimensonal map.