In general, the soils in Northeast Thailand are moderately to very strongly acidic with low organic content and low fertility. Improvements in soil quality are needed to promote better teak growth in the northeast of Thailand. This study aimed to investigate the growth performance of a 6-year-old teak plantation under various soil improvement methods at the Northeastern Forest Seed Center, Ban Had District, Khon Kaen Province, Thailand. Five different soil improvement treatments were applied as follows: control (no treatment); 2) dolomite application (400 kg/rai; 6.25 rai equals 1 ha); 3) dolomite (400 kg/rai) and organic fertilizer (1 kg/tree); 4) dolomite (400 kg/rai) and chemical fertilizer (15:15:15, 200 g/tree); and 5) mixed fertilizer (dolomite + organic fertilizer + chemical fertilizer at (15:15:15, 200 g/tree). The trees were planted 2 m × 4 m apart. The height and diameter at breast height (DBH) of the trees were recorded. The results showed that there were statistically significant differences in height but not in DBH among the different treatment groups at 6 years after planting. The plots with both dolomite and chemical fertilizer had the greatest height and DBH with averages of 12.3 m and 11.94 cm, respectively.