In the 10 years from 1987 to 1996, the yield of Thai maize hybrids, especially single cross, was significantly higher than that in the past 10 years. The yield of hybrids increased every year. The highest yield of suwanl was increased by 28.1% ~ 61.0%. In the first two years, the highest yield was triple cross, but in the following years, the highest yield was single cross, with an average yield of 9.0 ~ 9.5 T / ha. The yield of single cross is 35.4% higher than that of free pollinated variety and 4.2% higher than that of other hybrids. Its net income is 6445 baht / ha, 52.7% higher than that of free pollinated variety and 7.3% higher than that of other hybrids. In addition, the germination rate and seedling activity of single cross are very good, and few weak seedlings are produced by mechanical single seed sowing.