A thermal paper is described for the formation of images in thermal printing equipment and their manufacturing process, using high smoothness paper as a base or substrate. The thermal paper object of this invention is more economical and has a fully-acceptable performance. The high smoothness non-coated base paper has a greater high smoothness superficial finish than uncoated paper, and this development had not previously been used industrially for this purpose, since on trying to use the state of art of the process coupled with uncoated paper characteristics, the result was a low quality product. Hence, until now base papers had to be used with a previous coating the preparation of which increased production costs due to finished product characteristics, such as heavier weight (weight by square meter) and also a higher caliber.