The national infrastructure construction projects in Laos suffer from systemic inefficiencies caused by persistent delays and overspending. This research study evaluated the application of Lean Construction (LC) tools to improve project management processes in the Lao construction industry. Data was collected from 117 industry professionals (based on a mixed methods approach), including contractors (45.3%), owners (29.1%), and consultants (25.6%) across this population, which constitutes a substantial pool of expertise, with over 42% of respondents having over a decade of professional work experience. Results showed that ‘Compensation and land acquisition delays’ was the top factor that affected time (SI=83.33) and cost overrun (SI=84.62), with ‘owner-side payment delays’ and external material price volatility being the second and third most significant drivers. Importance-Performance Analysis (IPA) statistical analysis exposes a positive perception gap where very significant conviction exists to apply Lean to improving the efficiency (RII=0.844), however, the technical knowledge of basic tools as Visual Management (RII=0.368) is very poor. Inadequate training and educational programs are the biggest challenge to implementation (RII=0.742), and government policy is considered to be the key enabler (RII=0.798). The research paper presents an incremental "Crawl-Walk-Run" strategy in the form of a strategic roadmap that will prioritize the initial rollout of 5S Methodology and Last Planner System, followed later by the medium-term integration of BIM. For the sustainable development of the construction process in Laos, this study results in a call to move towards implementing Open-Book Collaboration and IPD (Integrated Project Delivery) over a traditional, "culture of blame" for construction and thus sustainable success.