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:

gan khor gan kor gangkor gang kor kangkor kang kor

kan khor

Min nan:

艰苦

poj:

kan-khó͘

expand for details Detailed etymology

definitions

adjective

  1. hard; difficult; arduous; troublesome
  2. Being Chinese, he merely remarked in a resigned sort of way: "Ang moh hor guah kan khor". Which is the nearest we can do towards phoneticising the curious gutturals that explained how the Europeans make unnecessary trouble for other people.

    — 1911 December 15. The Straits Echo (Mail Edition), “ANG MOH HOR GUAH KAN KHOR.”. p.1052


other credits:

Sam for the suggestion.