This is one of your best trees that you are counting on being worth something in the future. It is characterized by good form, quality, height, and diameter.
When thinning, you want a good stand of crop trees remaining. If, after a thinning, you have less crop trees remaining than poor trees, you were probably high graded. It is imperative that when you thin, the proper trees are targeted for harvest.
I have seen some tracts lately that are candidates for thinning—stocking levels are good; tree heights are excellent; diameters are big enough. However, in the case of a couple of particular tracts, there are very few crop trees while there are a lot of trees that are very poor quality trees marked by poor form. Both of these tracts, incidentally, were naturally regenerated—not planted. When you thin a pine stand where there are very few good crop trees, in essence, you will be growing poor quality trees bigger—you will be growing pulpwood trees into bigger pulpwood trees.
When there are not sufficient crop trees, it is better to totally harvest the stand and then reforest with good quality loblolly pine seedlings. There is very little benefit of growing pulpwood trees into bigger pulpwood trees.
Note: When you elect to not reforest by planting good quality seedlings, you are at the mercy of the seed stock of surrounding trees and of any seed that came from your trees in the harvest area. Whatever they are, that is what you are going to get.