Abstract: A thermal recording medium comprising a ultraviolet absorber precursor represented by formula (1-A) or an image forming compound changing hue and an acid, which is high in thermal sensitivity, recordable with such a low output laser that no ablation takes place even when a thermal heat mode image recording system using a laser is utilized, requiring no different receiving sheet, and excellent in keeping quality: ##STR1## wherein P represents a protecting group for a hydroxyl group which is deblocked by heating to 250.degree. C. or less in the presence of an acid; R.sup.1 and R.sup.2, which may be the same or different, each represents a substitutable group; and 1 and m each represents an integer of 0 to 4.