I am from India and have recently qualified in a PhD entrance examination. My specialization is English language teaching (ELT). I have to fill in an admission form including my research topic soon. Can you please suggest to me two or three topics on ELT?

First, as someone who has served on PhD program admissions committees, I would suggest that the point of this part of the form is to help people on admissions committees see if your research interests are a good fit for the department. This means that you need to spend time thinking carefully about a topic in which you would like to immerse yourself for the next 4 to 5 years rather than just seeing it as a hoop to jump through.
Your first way of narrowing your choice of research fields might be by types of student. You could focus on primary school, secondary school, university, or adult learners. You could also think about different types of English. Teaching migrants who aim for near native fluency is different than teaching business English or English for tourists or a reading knowledge of English for graduate students.  Also, students' own backgrounds and native languages raise different pedagogical issues. You could also, for example, blend TESOL and disability studies by focusing on teaching English as a second language to deaf students or students with other disabilities.
Another important and growing area is computer aided pedagogy of various sorts. Increasingly, education is delivered online to remote students. Research and specialization in online TESOL pedagogy (especially a pedagogy that can be implemented on mobile phones) is a growing area and particularly relevant to India.
Finally, "gamification" is an important area of study within language pedagogy. You could develop research on how to gamify TESOL for specific student populations.