A heat developable light-sensitive material comprises a support, a light-sensitive layer and a non-light-sensitive layer. The light-sensitive layer contains silver halide and a reducing agent. The non-light-sensitive layer contains a cyanine dye represented by the formula (I) or a salt thereof and a base precursor: in which R1 is hydrogen, an aliphatic group, an aromatic group, —NR21R24, —OR21 or —SR21, each of R21 and R24 independently is hydrogen, an aliphatic group or an aromatic group, or R21 and R24 are combined to form a nitrogen-containing heterocyclic ring; R2 is hydrogen, an aliphatic group or an aromatic group; R3 is an aliphatic group; L1 is a methine chain consisting of an odd number of methines; and each of Z1 and Z2 independently is an atomic group forming a five-membered or six-membered nitrogen-containing heterocyclic ring. A heat development image forming process, a thermal image recording material, a thermally decoloring image recording process and a process for decoloring a cyanine dye are also disclosed.