If the car is yours and not owned by the bank, you can drive BUT there is hell a lot of paperwork involved. First, in order to drive to Singapore, you need to bring the car to Malaysia first, pay insurance and road tax, get your car plate sticker with English letters, check that your window tint is not too dark and so on. Then, at Johor Bahru checkpoints to Singapore, you have to get an Autopass card. I've driven Malaysia registered vehicles in Singapore and Thailand. I've driven Singapore registered cars in Malaysia. I've driven Thailand registered vehicles in Malaysia but not in Singapore, so not sure what you need to bring to get the Autopass. For Cambodia, I think it's not permitted to bring Thai registered vehicles officially. Better take a road trip within Thailand only.