S$8888 / month. It's an auspicious figure, no ?

I think it's quite low.
but i'm not familiar with sales.

white card is the card that you filled in when you enter singapore.

it's too low. 1.6 1.7k is like STPM qualification job

knowing an extra language will always be an advantage

Not really.

Whether you're underpaid or not depends on the options available to you.

If there is someone else who is willing to pay you more than 1.7K, then you're underpaid. If you have no other offers and nobody else is interested in you, then you're not underpaid. You are ONLY paid... 1.7K.

In a word,.. no.

Assuming you currently have no proficiency in Japanese, the time and effort you need to expend in order to learn Japanese to a professionally acceptable level is way too high, compared to the return or advantage that you will gain from being able to speak Japanese in Singapore.

If you want to learn a language, I suggest to concentrate only on English and/or Mandarin.

If you are good in English, learn or improve your Mandarin.

If you are good in Mandarin, improve your English.

If you're half past six in both English and Mandarin (like 90% of the Malaysians here), then improve your English first before improving your Mandarin.

If you are very very good in both English and Mandarin... don't waste time and effort learning any more languages at a professional level. Using that time and energy to get a professional qualification or getting a higher degree will yield much better return on investment.

Well, get more data points first before concluding you're underpaid. Who knows, the other companies might only offer you 1.5K or 1.6K.

Ermmm... for business writing in a MNC environment... your English needs some work.