I have been offered a job but the boss said he can't provide an appointment letter and designation as per my application.

At the same time, he mentioned that he wouldn't provide the designation as per the application. He can only give me a suitable designation after I serve the company for a few months. I applied for the Social Media Executive position. I am very confused about whether I should accept this offer because it doesn't include an appointment letter or any designation. He only mentioned verbally that his employees don't have an appointment letter but only an offer letter. He has yet to come up with an appointment letter. It is a company that provides foreign workers to all sectors and also offers consultation regarding labor law. Please advise.

To me, it appears very murky and without even an appointment order, no use for the future. I would suggest, if you have a better option, try that. Before that, have due diligence done, and above all, if this is for a job offer from abroad, I have little knowledge about HR practices there. Exercise due caution, please.