Thailand boasts a robust ESL system in both public and private schools, where students learn various subjects from native speakers in the English language. Foreign language classroom anxiety (FLCA) is a subject that is relevant to ESL instruction and learning. This study assesses associations between FLCA and academic performance in English and math subjects at a Thai government school which is in its second year of employing native English speaking teachers. 424 students were administered FLCA surveys, which were compared to English and math exams. Moderate-high FLCA levels were found in the sample, with no difference between an immersion group and non-immersion groups. A weak, negative correlation was found between FLCA and English performance (r = -0.163). Thai language math exam scores were significantly better than English language math exam scores. No correlation between FLCA and math performance was found.