It is both because he is caucasian and a postman.
Being a caucasian, he naturally has higher status in Singaporean
than Singaporeans.
Also being caucasian, and a blue collar worker, he may have a
laid back personality, while being friendlier and more outgoing
than the average Singaporean.
Sadly, one of the reasons so many educated asian females marry
white men is that asian guys are very much the same- studious mummy
boys, focus on money, cars etc, while white men have far wider
interests due to lack of political censorship and freedom to
explore music and arts, and even to NOT go to poly or uni. So white
men allow asian women to escape the asian culture somewhat. It's a
bit of truth to the white man fantasy of helping asian women escape
the repressiveasian culture.