I hope you have reviewed the provisions of Rule 50 of the ESI (Central) Rules, 1952. The proviso to the said Rule states that "the wage limit for coverage of an employee who is a person with a disability under the Persons with Disabilities (Equal Opportunities Protection of Rights and Full Participation) Act, 1955 (1 of 1966), and under the National Trust for Welfare of Persons with Autism, Cerebral Palsy, Mental Retardation, and Multiple Disabilities Act, 1999 (44 of 1999) respectively shall be..."
Based on these provisions, it appears that ESIC may not be able to assist you in continuing your coverage under the said Act if your current wages exceed the coverage limit of Rs. 15,000 per month.
You may need to contact the relevant authorities in your area established under either of the above two enactments (based on your disability) to obtain the necessary disability certificate. Afterward, you can request your current employer to maintain your coverage under the ESI Act until the prescribed wage ceiling of Rs. 25,000 per month, as currently specified for individuals with disabilities.
If you have any uncertainties, I recommend presenting your case in writing to the Regional Director (Benefit Branch) of ESIC in your area with all the relevant details and requests.
According to Rule 51-A of the aforementioned rules, the employers' share of contribution in such instances is to be reimbursed to the ESIC by the Central Government. Therefore, in my view, it is vital to obtain a disability certificate under either of the above-mentioned enactments (as applicable to you).
Thank you.