Unfortunately traversing SE Asia is no longer an easy process as it once was, you didn't state where you planned to enter China but whichever entry point you will need a guide and a Chinese driving license (although an IDP may suffice). i would suggest you contact Jah @ Ride China who can give you all the correct information and costings on the China leg.
Reaching Boten in Laos, you may be able to enter on a Temporary import which would give you a maximum of 30 days in Laos (you must request this at the time of entry if required 15 days being the standard period). It is also possible you may require a guide or at least pay for some paperwork from a tour company to travel, Jah @ Ride China may be able to help on this.
Exiting Laos to Thailand, up until early last year, overlanders could travel easily through the Kingdom, again times have changed and you will require a guide to escort you to the Malaysian border, i would suggest you contact one of the many Facebook groups dealing with overland travel in Thailand amongst others, things change often and we hear stories of riders crossing through Thailand with no need for a guide of any kind then the next day a different picture .
Maybe Schmalick already is in China?
Anyhow - entering Laos might require you to pay a company for permits to travel through Laos. I entered Laos fro China at Boten around 4 years ago and at that time we didnt ned any permit. It was just a TIP and then go! You will most certainly get a TIP also now and dont forget to buy insurance.
Entering Thailand - since 2016 they have required a mandatory permit and guide through a certified travel agency. But the enforcement of these new laws seem to have been quite accidental and floppy. And the best is that it seems to be easier and easier to pass a border without having permits and guide.
This facebookgroup was created for sharing info about the new laws in Thailand: Thailand - New regulation affecting overland travellers on foreign vehicle
Contact David Goodchild in this group, he runs a little overland pit stop near Pattaya, around two hours southeast of Bangkok. He have helped many overlanders into Thailand without permits and guides - legally.
For Malaysia it should be quite straightforward - but you will need a Carnet. Buy insurance at the border and go!