Are you Malaysian-Chinese? I think your surname (last name) is actually "TAN"

Malaysian passports are very confusing and inconsistent as to which part of the name is your first name, middle name and last name. Unlike other countries, they do not use separate fields for Last/Family and Given names.

What does the machine readable line (the part with the < symbols) at the bottom of the passport data page say?

TAN<<JOHN<WEE<KIONG (I don't think Malaysian passports use << as this is a separator between the surname/lastname and the other names which most other countries use)
or
TAN<JOHN<WEE<KIONG
or
JOHN<TAN<WEE<KIONG
??

If TAN<<JOHN<WEE<KIONG, (Note the << being the "separator" between Surname/Lastname and given names)
then ticket should read either
TAN/JOHN MR
OR TAN/JOHN WEE KIONG MR

If TAN<JOHN<WEE<KIONG,
then ticket should read either
TAN/JOHN MR
OR TAN/JOHN WEE KIONG MR
OR TAN JOHN/WEE KIONG MR
OR TAN JOHN WEEK/KIONG MR

If JOHN<TAN<WEE<KIONG,
then ticket should read either
JOHN/TAN MR
JOHN/TAN WEE KIONG MR
JOHN TAN/WEE KIONG MR
JOHN TAN WEE/KIONG MR
ETC.

In the above examples, anything to the left of the "/" would be your surname/lastname and anything to the right would be your given names(s).

As long as your ticket follows the same order as the Machine Readable Line then you should probably be fine (as most check-in agents would swipe your passport to pull up your reservation during the check-in process).

Even if the order may not be correct, they may still be able to find you by manually searching the passenger list. If this is the case, you will have problems using any automated check-in kiosks that scan your passport to find your reservation.