If you have completed class 12th (10+2) with Physics Chemistry and Maths (PCM) you can directly apply for AME. You do not need to first do an engineering degree. If instead you have a 3-year engineering diploma (in any stream from an approved institute) that also makes you eligible for AME.
If you finished 12th with PCM you don't need to wait you can start AME right away.
If you did a diploma already you are also eligible.
This flexibility helps you begin your aviation career early saving time and effort.
You avoid the extra years and cost of a full engineering degree and still become qualified to work as an AME.
Since the demand for licensed maintenance engineers is high starting early gives you a head start in gaining experience.
You must have 10+2 with Physics Chemistry and Maths without PCM you won't be eligible directly after 12th.
Some institutes require a certain minimum percentage in 12th (e.g. around 45-50 %) for admission.
Medical fitness is important. For example color vision issues or serious physical disabilities may disqualify you.
AME involves serious commitment technical learning and hands on practical work so you need interest in mechanical/aviation systems and willingness to work in sometimes challenging schedules.
If you are in 12th with PCM and want to become a licensed maintenance engineer go for AME after your board results. If you don't have PCM you can still enter AME by taking the NIOS exam for the specific Maths subject.