The theory of collective Thomson scattering from high-temperature high-density plasmas is revisited from the viewpoint of plasma fluctuation theory. Three subtle effects are addressed. The first is the correction of the first order of v/c, where v is the particle velocity and c is the light speed, the second is the plasma dielectric effect and the third is the finite scattering volume effect. When the plasma density is high, the first effect is very significant in inferring plasma parameters from the scattering spectra of electron plasma waves. Without the inclusion of the correction, the electron temperature may be significantly underestimated. The second is also notable but much less significant. When the size of the scattering volume is much larger than the probe wavelength, the third is negligible.