You need a Certificate of Residence from CM immigration. Sometimes you can get one next day for 500B yourself. I hate going to immigration and with 2 trips needed I just paid a nearby agent 1,500B all in.
You also need a medical certificate. Any clinic will do this. I paid 30B and the receptionist filled it out as I stood at the desk!
Take these along with your own licence, IDP and passport to the Provincial Land Office down Hang Dong Road. As well as originals you will need photocopies of everything. You need to watch a video and check you know what colour traffic lights are.
It is a bit of a faff but the staff were helpful, just stay patient.
You may be able to book online the video slot which will save time, I didn't.
Can't remember the licence cost, think it was 100B or so.
Good luck.