Buy a license

Are you talking about a "driver" license?
If yes, I can tell you something.
Last month I went to the ministry to take the exsm.
It was a special one for foreigners....one a week.
On about 50 peoples that day there were something like 40 Chinese.
I have been told that a lot of Chinese people are now doing that... coming in Cambodia to get the licence.
I think that if they had a way to get it faster... I mean I secured way also.... I think they would have done it instead of take the exam and risking to fail.

what procedures are required to purchase land in Cambodia as an expat with e visa and bank account and drivers licience.

To purchase a land as an expat? In Cambodia?
No way...
But an expat can be partly owner of a land...
I mean, if your are an expat, you have to create a company. In this company you will have only 49%... the 51% have to be khmer. Than, this company can own a land.
The only other way is a 99 years rental contract. .. but you will not be the owner. ..
One or two other ways... but against the law... so no need to talk about those ways