Can I re-enter Thailand by land after extending my stay in immigration?

a Short question, I entered Thailand by land once. Based on that the answer will be no problems. Than a reply of the OP, : " I was refused for the reason that I have too much return for 3 years.". I can tell you that you were not refused entry with the reason too much return for 3 years, simply based on the fact that that reason does not exist. The reason of your denied entry is stamped in your passport. I close the commenting, we can give advice but we need some basic information to work with.

Yes

You are allowed 2 land crossings per year. But you can be asked to show B 20k, flight out and accomodation. Worst that can happen is that you must walk back to Laos at the border.