OBJECTIVE Hypokalemia is highly prevalent in chronic peritoneal dialysis (PD) patients worldwide, particularly in Thailand. This study aims to investigate the major determinants of hypokalemia in Thai PD patients. METHODS A cross-sectional study was performed in chronic PD patients at 4 PD centers in Bangkok, Thailand. Hypokalemia was defined if the average serum potassium level during the last 3 consecutive visits was < 3.5 mEq/L. Patients and/or their caregivers were asked to perform a 3-day dietary food record and take pre- and post-meal pictures following the instructed protocol. Daily dietary nutrients, including potassium, were estimated by a single dietician using INMUCAL-N software. Total potassium excretion was determined by 24-h PD effluents and urine collection. Intracellular and extracellular water values (ICW and ECW, respectively) were measured by electrical bioimpedance assay (BIA) to indirectly explore the role of intracellular potassium shift in hypokalemia. RESULTS Among 60 eligible PD patients, 19 (31%) had hypokalemia. Hypokalemic patients had significantly lower dietary potassium intake (24.4 ± 11.1 vs. 30.5 ± 9.4 mEq/day, p = 0.031) and lower total potassium excretion (28.5 ± 8.4 vs. 36.7 ± 11.2 mEq/day, p = 0.006) compared to normokalemic patients. Both groups had comparable values of ICW and ECW. On logistic regression, there was no significant correlation between hypokalemia and daily PD exchange volume, total Kt/Vurea, residual renal function, concurrent medications (insulin, diuretics, renin-angiotensin-aldosterone inhibitor, and beta-blockers) or ICW. Low dietary potassium was an independent risk factor for hypokalemia. CONCLUSIONS Low dietary potassium intake, rather than increased potassium excretion or intracellular shift, is the major contributing factor of hypokalemia in Thai chronic PD patients. Dietary intervention or potassium supplement protocol should be implemented.