Depends on the company culture of course, but the places I’ve been in Malaysia have dressed fairly casually (lots of polos or casual collared shirts but a t-shirt was fine), what you describe wouldn’t be a problem. The only thing to pay attention to is that if your office has Muslim people it is generally respectful to wear long pants instead of shorts (I went to a factory in Malaysia once and wore shorts because it is ungodly hot and my next colleague to visit got a friendly reminder to wear long pants).