You may show your appointment letter, bond, all communications in your record, to a competent and experienced service lawyer and give inputs in person. You lawyer may confirm that you fall within the category of workman.
Have you been provided any training that added to your skill or qualification?
Has any training completion certificate been supplied to you?
What was the cost of training per person/on you?
For how long you have worked with the company after the training and do you have any data on revenue and profits generated by you for the company?
What is your designated in your appointment letter? You may obtain copy of certified standing orders of the company which are to be displayed at the entrance, or may be available at HR page of the employee portal.
You may also obtain employee rule book, which is to be circulated/supplied to employees.
Or you can demand these from concerned HR personnel. If these are not supplied by Hr you may write under acknowledgment to good offices of your appointing authority, MD with a copy to Head-HR.
You may obtain printouts, forward copies of all emails, letters which can be later useful to you. You may obtain SE Act applicable to your state from Labor website or market.
You should have consulted elders in the family, competent and experienced well wishers, trained legal mind before signing on the bond.