Short answer. As a rule, no. Article 18 bans direct-hiring: no employer may hire a Filipino worker for overseas employment except through the Boards and entities authorised by the Secretary of Labor. Narrow exemptions exist for the diplomatic corps, international organisations and employers the Secretary allows.
What the law says
No employer may hire a Filipino worker for overseas employment except through the Boards and entities authorized by the Secretary of Labor.
Labor Code, Article 18 — Ban On Direct Hiring. Read the full provision →
The prohibition is addressed to the employer
The wording is flat: No employer may hire a Filipino worker for overseas employment except through the Boards and entities authorized by the Secretary of Labor. Note who is being told what. The duty falls on the employer doing the hiring, not on the worker accepting the job, and it is expressed as a channel requirement rather than a paperwork step. Hiring outside the authorised channel is not a defective hiring that can be cured by producing a good contract afterwards; the provision treats the channel itself as the thing that had to be used.
It only reaches overseas employment
The ban is confined to hiring for overseas employment, which Article 13 defines as employment of a worker outside the Philippines. A foreign-owned company hiring somebody to work in Manila is hiring for local employment and is not within this provision at all — its obligations come from elsewhere in the Code. What the ban catches is the arrangement most people mean by a direct offer from abroad: an employer outside the country recruiting a Filipino to be deployed there, without an authorised entity standing between them.
The exemptions are narrow and are not self-declared
The same article exempts direct-hiring by members of the diplomatic corps, by international organisations, and by such other employers as may be allowed by the Secretary of Labor. The first two are defined classes. The third is not a category an employer can put itself into by asserting that its case is special — the exemption exists only where the Secretary has allowed it. So an employer saying it is exempt is making a claim that can be checked, and checking it is a good deal cheaper than discovering later that the hiring never went through a channel that recognises it.
If you already have a direct offer in hand
Do not treat the offer letter as the whole picture. Find out which entity is actually processing the deployment and what document it holds; find out whether the employer says it falls in one of the exempt classes and on what basis; and keep every message, contract draft and receipt for anything you have paid. The recurring pattern in these cases is a worker who has paid money and surrendered documents to somebody whose standing was never established. A lawyer can assess that quickly, but only from the papers themselves.