This paper aims to elaborate the strategy for operational and cost efficiency improvement by providing an example of a successful case of rig selection strategy for Hydraulic Fracturing Operation in S1 oil field Thailand. The integrated workflow proposed involves all concerned parties to specify the scope of work, analyze internal and external strengths and weaknesses, evaluate possible scenarios, and identify the procurement strategy. As a case of rig selection for fracturing operation in the heterogeneous sandstone, committing the number of candidates before drilling is impossible. Therefore, the typical criteria for fracturing rig selection consider rig move mobility and flexibility in candidate selection. However, in a proven area, the uncertainty of candidate confirmation is manageable. Reservoir engineers provide the number of candidates in 3 scenarios for sensitivity analysis. SWOT analysis and the market survey reveal the possibility to improve both performance and cost by using a warm-stack skidding rig instead of a truck-mounted rig. The sensitivity analysis by using the historical data of each type, indicates that the number of candidates and rig cost play a significant role in cost saving. As a result of analysis and strategy, the operation performance improvesby 34% (2 months reduction) leading to cost-saving by 1MM USD or 24% of the time-dependent cost.