Many people have driven between Singapore and China
The most challengeable route is the part from north boarder of Thailand to Hanoi, you'll need to pass through the rough road with little signs in Laos. Many people chose to drive to Hu Chi Ming City and then drive along the way to the boarder between Vietnam and China. This route is much further.

Your route would be Singapore--Malaysia--Thailand--Laos--Vietnam--China or Singapore--Malaysia--Thailand--Cambodia--Vietnam--China

For other information, you must get to know the location and phone number of car service points on your way, thus you can get the help immediately when there is something wrong with your car.
You also need a permit of every country you'll passing by, you can apply for it in the Embassy of those countries.
You also need an insurance for your car, highway map of the countries, you can buy the map of Thailand in the north part of Malaysia.