If s/he is of Chinese heritage, then I would suggest putting the family name as name1, then the most significant given name as name2 and forget the rest.

If of Christian and/or Indian heritage then name1 should be his given name and the family name should be name2, and I'd still forget the rest unless he is routinely called by another name and it's in the passport. Forget a/l, s/o (son of) and what-not.

If Muslim then typically you enter Abdullah bin Raffie or Abdullah Raffie (or whatever), it doesn't much matter.

In short, the easiest way to handle this is to ensure at least 2 names are in there, the given name and surname, and it doesn't much matter what order they are in, or what other names are used. If there are two family names or they are hyphenated, never leave out the father's name in full.