Hi, there is no clear answer for your question

yes i would recommend u hire tax agent, but the asking will be depend on them and their finding, they dont do audit, it is auditor job to audit, different stuff

as for the charge, hard to tell, no one can really answer

dont think u should engage every month but it is good to have a reliable tax agent just in case policy change

u still need accountant to work for you, dont pay them peanut tho, decent enough above market industry, they are also helping auditor and tax agent too, keep proper account filing and document now is very super important thanks to e-invoice lhdn especially the consolidate e-invoice, if the lhdn think u lari tax, they will immediately ask document, now they are on the wild hunt.

hope this help.