I can get a job consulting for a Thai real estate company, but just for 4 hours a week, maybe 8 hours. Would it be possible to get a non-immigrant visa and a work permit on the basis of such a small contract? Also, is there a minimum amount of money that one would have to earn to be eligible? Are there other things to consider in this case?

I guess the million dollar question is whether the company concerned is prepared to do all the documentation for you to get a WP ?

On face value yes it would be possible to get one, however below a certain threshold of earnings, typically THB 50,000-60/month you will not be able to get an extension of stay and will therefore have to visa run every 90 days