In this paper we report on experiments performed to estimate the nonlocality of the photothermal non-linearity in thick dye-doped nematic liquid crystal (DDNLC). We have studied the interaction of two counter-propagating self-focused laser beams parallel to each other. From this experiment, a rough estimation of the width of the induced index profile with respect to the beam size is derived (non-locality). In a second part, we report a set of results concerning the tuning of this nonlocality. As the laser light is chopped and for power large enough, the beam is self-trapped in a narrow isotropic channel, the length of which depends on the input power. We describe an original experiment of self-guiding of light by the use of such an effect, namely bent isotropic channels.