 Bang Krathum lies in the Nan Basin, which is part of the Chao Phraya Watershed.The town of Ban Bang Krathum is on the tambon's chief watercourse, a canal which winds through farms heading north-east to Ban Bang Kranoi in Nakhon Pa Mak, where it joins the Wang Thong River.The canal splits once between Ban Bang Krathum and Ban Bang Krathum, where a smaller branch leads due north to Ban Bueng Lam in Nakhon Pa Mak.