HI Edward,
Further to your question, we don’t have a fixed matrix that shows what is required for each higher class. The first step would be to discuss with the local authorities that we wish to change our status/ scope of work.
K Atchara would be the person to make this first contact, after that further discussions together with the engineering dept. would take place to see what needs to be done.
Apart from physical modifications to the buildings there would also be statutory changes for the company meaning more/other audits/ISO standards/taxations/….