I'm not sure I understand your career goals. Teaching ESOL in the US doesn't require you to be a professor, because ESOL teaching happens at the K-12 level, community centers, and so on. US universities require students to be proficient at English before they enroll. Some faculty do specialize in teaching writing to students for whom English is not a first language, but those students are already reasonably fluent.
Teaching English in a country where English isn't the first language is a different matter. In countries where English is widely spoken, e.g. most of Western Europe, you would need a PhD in English +, usually, fluency in the language of the country where you'd be teaching. In some cases the latter wouldn't be a requirement--one of my (American) students was offered a job in Sweden with the understanding that he would learn Swedish over the course of a few years. But more commonly, English professors in Germany, Japan, Spain, India, etc. are natives of those countries educated in the US or the UK.