This project involves the construction and improvement of Highway No. 21, from Lom Kao District to Loei Province, in the section from Rong Chik Sub-district to San Tom Sub-district, Section 2, between km.361+500.000 and km.367+750.000, with a total distance of 6.250 kilometers. The main work includes the removal of existing structures, earthworks, subgrade work, pavement work, structural work (bridges, box culverts, drainage systems), miscellaneous work (signs, lighting), and environmental management. The main pavement is Asphalt Concrete, with some sections being Joint Reinforced Concrete Pavement. The project includes the construction of new concrete bridges, the widening of existing bridges, the construction of box culverts, and subsurface drainage systems. Other works include the installation of concrete barriers, guard rails, sidewalks, and landscaping. Emphasis is placed on materials that meet standards and are environmentally friendly.