Should i buy a car by installment in KL?

I don't think you will be able to get a car on installments (or a car loan) without having developed a good credit history in Malaysia and having a higher income. Suggest you save up and pay cash for a vehicle.

Maybe an Perodua  Axia or Myvi. For a 9 year loan you'd be paying around RM750/month. Call the bank up and ask for the qualifications needed as an expat. But at RM3500 average, you wouldn't have much left to spend/save after taking into account your rental.

Owned three personal vehicles in Malaysia. From my experience;

I would assume you only want to know the financial part of purchasing a vehicle and not the rest. Firstly, do you intend to buy a 2nd-hand or brand new?

Should you choose to get a brand new vehicle, your options may be Perodua as they are affordable and reliable. You may opt to go for Toyota/Honda. They have excellent resale value. I would advise you to stay away from Proton. There is a reason Perodua is the hottest selling brand in Malaysia. These cars are designed and made from Toyota/Daihatsu models. 3500k to 4k a month is more than enough for you to afford any Perodua model.

Buying a car brand new, you would need to get a loan. Choices for loan would be 3 years, 5 years, 7 years, and 9 years. You may not be able to choose sometimes, the bank will determine which they would give...sometimes. You car sales agent would help you arrange these. To book a vehicle, you would need to pay a deposit of RM500.

Downpayment. Locals pay 10% of the car's total amount for downpayment, sometimes for promotion they can get away with 0%. However as a foreigner, you would be required to fork out 30% downpayment of the car's total value. For one of my vehicles, I only paid out 20%. But this is rare, prepare to pay the standard 30%.

To buy a 2nd-hand...you would want to check out Carlist.my or perhaps even Mudah.my. Process is more or less the same. 30% downpayment, RM500 booking fee, bank loan.

Btw bank loan in general have a 2.7% interest for vehicles. Credit rating is not that important. Either way they would ask you 30% downpayment and if your salary can't cut the monthly minimum, they would not give a loan. 

Try not to buy the entire value of a car in cash. When it comes to resell, you could possibly lose out. Toyota/Honda/Perodua have great resale value. The last time I sold my Toyota, it covered the remaining loan amount and enough excess to cover the 30% of the car I was going to replace it with.

Feel free to ask any more questions you might have.