Should I stay in my current job for the 3-month bonus or jump now?

From my experience, never let a 'hinting' promotion hold you back. I stayed one extra year waiting for a promotion that my manager kept promising and in the end they gave it to an external hire. If the new offer is confirmed with better pay and prospects, count the numbers properly. RM1,500 x 12 is RM18,000 a year, versus roughly 2 months bonus one time. Usually jumping wins over the long run. But do the maths for your own case, and if you leave, try to resign right after collecting bonus in Feb so you don't lose it. Get the new role's start date flexible if you can.

I would counter-offer first before deciding. When I got an outside offer, I told my current boss politely and asked whether the promotion could be confirmed in writing with a date. My boss actually matched part of the salary and gave me a proper title. If they only give more 'hints' and no document, that is your answer already. Also check the new company's reputation on Glassdoor and LinkedIn, ask people who worked there. A higher salary in a toxic place is not worth it. Take your time, this is your career, not a mamak order.