Can I become ESL teacher?

Before you decide on the appropriate qualification, yes think about whether or not you want to teach children or adults. Do you want to teach teach English to business people or to some other specialist group. Find the right college that will enable you to learn at the correct pace for you. Intensive courses are just that and do not allow you any real thinking time to assimilate the teachings properly. Go for an internationally recognised qualification and to one of the better schools teaching the course. That way you get the best possible instruction.