Patterns and driving factors of built-up land expansion in small provincial city in the Belt and Road Initiative: case study of Nong Khai City, Thailand

China’s Belt and Road Initiative is the twenty-first century megaproject that will boost urbanisation and elicit expansion of new built-up land. However, little understanding exists concerning the expansion of new built-up land in small cities that will encounter urbanisation unavoidably. Thus, this study aims to clarify the patterns and driving forces behind built-up land expansion during the 1997–2017 period using Nong Khai City, Thailand–which has become an international hub in the Pan-Asia Railway Network–as a case study. Land-use maps were generated based on Landsat Satellite images and used to examine built-up land expansion, and driving forces were clarified through logistic regression using 16 independent variables based on four groups of driving factors. The findings indicate that built-up land expansion was the predominant pattern of land-use changes, with agricultural land transformed the most. Most independent variables affected the expansion with the same relationship, but magnitude varied during different periods. Socioeconomic and neighbourhood and spatial interaction factors were the most powerful driving forces during the 1997–2007 and 2007–2017 periods, respectively. While the designation of built-up areas under the spatial policy factor exerted a moderate influence on built-up land expansion over time, the influence of almost all the variables of biophysical factors was weak, except distance from the Mekong River. In the future, city planners should consider controlling the expansion of built-up land into agricultural land and conserve agricultural land around cities.