Commonly found variants; note these may range from acceptable alternatives to non-standard forms or incorrect spellings*.
* Singlish is a largely spoken creole, and as such descriptivism (recording forms that reflect actual pronunciation in spoken language, or as appearing in the linguistic corpus) is more pertinent than strict prescriptivism. Nevertheless, the use of more standard forms (or for words originating in languages with Latin script, such as Malay, accurate to the original spelling) is recommended and encouraged.

also can:

des why das why

that's why

English:

that’s why

expand for details Detailed etymology

definitions

interjection

  1. used in response to something said that one agrees with; ’precisely!’; ‘exactly!’; ‘I know, right?’; ‘that’s what I’m saying’
  2. - Wah piang, this match damn boring one sia.
    - That’s why.


usage notes

In a sense, used to agree with something another has said while entirely omitting having to provide substantiation for their point via an explanation or reason; an expression of ‘yep, no explanation needed’.