Is there any chance to get S-Pass for Vietnamese with Japanese major?

The criteria are the same for all applications - and there is certainly no discrimination against people who speak Japanese or are from Vietnam.
The processing time can vary greatly, though, from a few days to several months. Read the related threads on this forum to understand why!

Thank you for your advise

Unfortunately  my application was rejected today with the reason: "The work pass is for the foreigner to work as an employee for the direct employer only and not to work for another company/client"
- my position work onsite in client company. My company suggest to make an appeal , so is there any chance for my application get approve ?

You can only get a work pass to work for a Singapore-registered company.
If that company sends you to provide services at a client location, this is o.k. and in fact common.
So I have problems understanding the rejection reasoning.
Which company is your employer? What is their client you are supposed to serve?
Is it maybe possible for this client to hire you directly?

My employer is Adecco and they provide service for Apple Singapore
(my position is work onsite in Apple).
They also have enough quota for apply S-pass so it's quite confusing for me

Adecco is a big and experienced temporary employment agency, so I am very surprized about this. Must be a specific case.