Being evil / Being an asshole / Having bad intentions
'cek ark' is a hokkien term, most commonly used among Singaporeans and is used to describe an individual.
An individual being 'cek ark' can be described as behaving in a way that is considered extremely obtrusive, often incurring the wrath of those around the individual by means such as verbal insults and the occasional fist to the face
Wah you see him so jialat already, you still laughing at him. You sibei cek ark!
Wahlao that teacher damn cek ark sia, don't want to let me pass the test.