The recent increase in dairy and cattle production in Thailand has increased demand for high-quality roughage, particularly corn silage. Although there has been a great deal of research on field corn, far fewer studies have focused on corn intended as silage. This study involved a field experiment that analyzed crop management methods, focusing on plant spacing and 8 of the field corn varieties most commonly used in Thailand. The objectives were to determine which plant spacing and variety produced the best forage yield and silage qualities of corn silage. The plantings were arranged in a split-plot Randomized Complete Block Design (RCBD) with four replications. The main plot contained two spacing (75×20 and 75×25 cm2), each with subplots of 8 field corn varieties (SW5, NS2, NS3, NSX982013, TE1719, WS6437, WS6440, WS6442). All plants received the same crop management care regarding soil conditions, water, fertilization, and weeding. The results showed plant spacing did not significantly affect plant height (cm) and ears per plant, but the narrower 75×20 cm2 spacing produced the highest fresh leaf yield (13 t ha-1) and dry stalk yield (4.5 t ha-1) (p < 0.05). At 75×20 cm2 spacing, the TE1719 varietal had more ears per plant than SW5 (the check variety). TE1719 had the best fresh ear, stalk, and total biomass yield at both spacing of all the varieties. With regard to silage quality, the plant spacing did not significantly affect the CP, ADF, ADL, ash, and pH of the corn silage. The study revealed planting TE1719 varieties at 75×20 cm2 spacing is more economical for farmers because it increases forage yields without negatively affecting the nutritional value of corn silage.