Correlated two-photon imaging, also known as "ghost" imaging, has attracted much attention and debate in recent years. The earliest experiments were performed with entangled light, and later with quasi-thermal light. Our group was the first to use true thermal (incoherent) light to demonstrate two-photon imaging and interference. We successfully realized lensless ghost imaging with true thermal light at 692.9 nm from the buffer gas in a hollow cathode lamp. The object was a mask with two pinholes separated by 3.66 mm. Furthermore, we analytically studied the effects of higher-order intensity fluctuation correlations on high-order ghost imaging and interference, and found that visibility can, in theory, approach the maximum value of 1 as the order increases to infinity. Our experiments on lensless high-order ghost imaging with a quasithermal light source for orders up to 10 demonstrate that visibility does indeed improve dramatically as the order increases. It is thus possible that high-order lensless ghost imaging with thermal light may find useful application where conventional imaging techniques are impractical or impossible to use.