The propose of this research was to present and describe the reliable for sex determination recent Thai skeletons using tibia bones and ulna bones. A sample of bones corresponding to Thai skeletons deposited at the Department of Anatomy, faculty of Medicine Siriraj Hospital, Mahidol University was analyzed. The sample consists of 20-90 years old adult individuals 52 Thai skeletons (male = 30, female = 22). Researcher also analyzed the existence of significant differences between the mean of both sexes for each of variables analyzed, applying the t-test statistic and discriminant analysis procedure of the SPSS software. It was not only we found that the mean and standard deviation of the tibia and ulna bones in male are more than female but also there were significantly differences between male and female (P < 0.05). The results of this research indicated that the accuracy separated for the best in male is the MTCL right 86.67% and the Total length of Ulna left 80% of female found that the accuracy is spot (DSBT) right. Tibia has the highest value 90.91% and the Total length of Ulna both the left and right Ulna with the Minimum Olecranon breadth side of the Ulna, which has an accuracy equal 86.36%

The result suggest that tibia and ulna are the one of choices that can be used for sex determination in forensic identifications.