Learning to teach during a teaching practicum has often been described as a challenging experience for student teachers; however, little is known how they overcome the challenges. Using teacher identity as an analytic lens, I investigated how two English-major student teachers in a one-year teaching practicum in Thailand constructed teacher identity. The data were obtained from interviews and shadowing observations. Thematic analysis revealed that teacher identity was developed earlier in biographies. The teaching practicum contributed to teacher identity development in three ways: (1) emotional responses to the practicum shaped identity, (2) practice shaped identity, and (3) symbolic entity as a reminder of being a teacher shaped identity. Additionally, the student teachers overcome challenges through psychological and technical supports from within and outside the schools. The findings suggest that teacher education should give careful attention to the teaching practicum as it contributes to the development of student teacher identity.