Vocabulary is a fundamental building block in the process of learning English. Many language departments in Thailand emphasize conversation and introduce students to complete sentences early in their curriculum, but that path leads to a plateau where students stop learning once they reach a certain level. That approach is based on the theory that this is the way we learn languages naturally, which is true but not relevant. Learning a foreign language purely through conversation works with children in an immersive environment, but that's not an effective approach for students who take English classes once a week.
Conversation training without vocabulary training doesn't work well for older students or adults because they already think in one language and they will try to translate between their first language and the one they're learning. That's why vocabulary training should always be included in the curriculum.
Conversation training should be balanced with vocabulary, pronunciation, and translation exercises. Reading and writing are also essential skills for students who will attend college or university. All of these skills should be taught in proportion.
California Accent offers vocabulary course in three areas. All of the courses focus on vocabulary. These courses can also be used to teach English to older students or adults. The Intermediate Vocabulary courses are ideally suited for high school students or adults who already have a working vocabulary of several hundred English words. The three courses can be used to introduce curious students to scientific terms.