  We report on the charged-particle multiplicity dependence of net-proton
cumulant ratios up to sixth order from $\sqrt{s}$ = 200 GeV $p$+$p$ collisions
at the Relativistic Heavy Ion Collider (RHIC). The measured ratios
$C_{4}/C_{2}$, $C_{5}/C_{1}$, and $C_{6}/C_{2}$ decrease with increased
charged-particle multiplicity and rapidity acceptance. Neither the Skellam
baselines nor PYTHIA8 calculations account for the observed multiplicity
dependence. In addition, the ratios $C_{5}/C_{1}$ and $C_{6}/C_{2}$ approach
negative values in the highest-multiplicity events. The negative ratios in the
most central p+p collisions at 200 GeV, similar to those observed in central
Au+Au 200 GeV collisions, imply the formation of thermalized QCD matter.
