This research aims to identify the effects of salinity from sodium chloride NaClon agronomic characteristics of Thai rice varieties as compared with a tolerant variety for salinity stress at the tillering stageThe experiment was conducted as a 4x3 CRD.The first factor consists of four concentrations of NaClThe second factor consists of three lowlandrice varieties, namely, Inpari 35 salttolerant rice varietyand two Thai rice varieties, Pathum Thani 1 PTT1and Chai Nat 1 CNT1The results showed the effects on all observed characteristicstillers, plant height, and score symptoms on plantIn the first week after adding salinity (three weeks after planting), the salinity stress initially affected leaf symptoms in all rice varietiesHowever, the salinity stresses severely affected the number of tillers per plant more than other traits at three weeks after adding salinity (five weeks after planting)Overall means of observed agronomic characteristics values of Inpari 35 generally showed higher values than PTT1 and CNT1 in one and three weeks after adding salinityInpari 35 also showed a lower reduction percentage compared with the normal condition; 0 mM NaClthan two Thai rice CNT1 and PTT1 at three weeks afteradding salinity, especially in the number of tillers per plant from the concentration of 50 mM NaCl onward