This study investigates patterns and characteristics of the surface urban heat island (SUHI) in Hat Yai City, a city located in Southern Thailand. In order to define urban and non-urban features from satellite images, an object-based classification was applied using Landsat 5 (TM) and Landsat 8 (OLI) for 2010 and 2020, respectively. Land surface temperature (LST) was extracted from the thermal infrared band of Landsat images as the main data sources for estimating SUHI variability over the period of 2010 and 2020. The spatial pattern and SUHI variation were then investigated using spatial analysis. The analysis of SUHI variation showed that the behaviour of LST depends on the land covers surrounding the city. In general, most LST in the urban areas were higher than surrounding areas in the study period. The response of SUHI to the increase in urban sites showed in both spatial and temporal variations. It indicates that SUHI intensity tends to slightly increase during 2010-2020 (about 0.41oC). Moreover, this study also pointed out that the densely built-up areas, and heavy industrial zones are the greatest contributors to SUHI of this city.