Abstract: [Objective] Columnar joints in basalt are typical structures formed during magmatic cooling and contraction. However, their formation mechanisms, internal structures, and cooling histories remain debated. This study aims to constrain the internal structure and cooling history of large basalt columns using integrated rock magnetic and paleomagnetic methods. [Methods] Detailed rock magnetic and paleomagnetic analyses were conducted on 49 oriented samples collected from two Pliocene basalt columns (up to 1.5 m in diameter) in the Bo Phloi section, Kanchanaburi, Thailand. Rock magnetic experiments include hysteresis loops, isothermal remanent magnetization (IRM) acquisition, first-order reversal curve (FORC) analysis, anisotropy of magnetic susceptibility (AMS), and temperature-dependent magnetic susceptibility measurements. Stepwise thermal demagnetization was used to isolate stable remanent magnetization components. [Results] Hysteresis loops and IRM acquisition curves show saturation below ~300 mT and a two-stage increase with increasing field, indicating contributions from magnetic components with different coercivities. FORC diagrams confirm pseudo-single-domain (PSD)-dominated magnetic domain states, with systematic differences between column margins and interiors. AMS results show that both basalt columns are characterized by sub-vertical minimum susceptibility axes (K₃) and sub-horizontal maximum (K₁) and intermediate (K₂) axes, with generally low anisotropy degrees (Pj < 1.05), indicating a primary near-horizontal magma flow fabric during emplacement and no evidence for vertical melt migration or internal convection. AMS parameters further reveal systematic spatial variations: marginal samples exhibit lower magnetic susceptibility (Km), lineation (L), and anisotropy degree (Pj), with predominantly oblate fabrics (T > 0), whereas interior samples show higher Km, L, and Pj values and predominantly prolate fabrics (T < 0). These differences reflect contrasting cooling conditions, with rapid cooling at the margins and slower cooling in the interiors. During magma solidification, the margins of the basalt columns experienced faster cooling, resulting in shorter time available for crystallization and preferred orientation of magnetic minerals, and consequently lower magnetic susceptibility and anisotropy. In contrast, the interior portions cooled more slowly and likely remained in a high-temperature plastic or partially molten state for a longer period, allowing magnetic minerals to crystallize more completely, become concentrated, and align under thermal contraction stress. Paleomagnetic results indicate that thermal demagnetization isolates stable single-component remanence carried by PSD titanomagnetite. Six marginal samples from basalt column A exhibit more scattered virtual geomagnetic pole (VGP) distributions and anomalous directions, whereas the remaining 43 samples show relatively clustered VGPs after tilt correction. Systematic variations in remanent magnetization directions and VGPs indicate that cooling did not proceed symmetrically or uniformly from the margins toward the cores, but rather followed an asymmetric, unidirectional regional cooling pattern, which was likely influenced by a localized heat source. [Conclusions] Based on integrated rock magnetic and paleomagnetic analyses, the main conclusions are summarized as follows. (1) The basalt columns from Kanchanaburi are dominated by pseudo-single-domain (PSD) titanomagnetite, and AMS fabrics with sub-vertical K₃ and sub-horizontal K₁ and K₂ axes indicate a primary near-horizontal magma flow during emplacement. (2) Marginal zones cooled faster, producing finer magnetic grains, lower anisotropy, and oblate fabrics, whereas interior zones cooled more slowly, allowing stronger magnetic alignment and higher anisotropy with predominantly prolate fabrics. (3) Systematic variations in paleomagnetic directions and VGPs from 49 samples indicate that post-jointing cooling was not uniform or symmetric, but instead proceeded as an asymmetric, unidirectional process across the basalt columns. [Significance] This study contributes to a better understanding of the cooling process of basaltic lava and provides new insights into geomagnetic secular variation.