Retainer contract for company physician - legal or not?

Hi! I'm wanting to be part of a multimedia company to be their company doctor. I'm PRC board certified and trained in basic occupational health and safety required by the DOLE. I was offered a retainer contract but have second thoughts as I know this will mean the absence of an employee-employer relation which has its good as well as bad points. From what I understand rule 1963.4 of the amended DOLE-BWC Occupational Safety and Health Standards prohibits employers from entering into retainership agreements for occupational health services but then most of the guys I know working as company physicians either have retainer agreements directly with the company or with a third-party contractor being engaged by the principal company for occupational health services. A law student I talked to says what he know is that the Labor Code allows retainer contracts but when I read the law myself it states in Art. 157 "Where the undertaking is non-hazardous in nature, the physician and dentist may be engaged on retainer basis, subject to such regulations as the Secretary of Labor and Employment may prescribe to insure immediate availability of medical and dental treatment and attendance in case of emergency." Now, isn't it the Occupational Safety & Health Standards is considered the document "prescribed" by the DOLE Secretary and, therefore, should be followed, i.e. retainer agreement for physicians to render occupational health services is unlawful?
Sirs, i'd be very glad if you can enlighten me on this as I have to decide whether to sign the agreement or negotiate further to be an employee of the company. Thank you.