## 1 Introduction
The application of SbPPs and GbGPPs have been reported not only in hydrologic modeling [23; 24; 25] but also in many other areas including, flood inundation modeling [26], drought monitoring [27], soil erosion predictions [28], etc. Considering the diverse applications of SbPPs and GbGPPs the assessment of the efficiency of the SbPPs and GbGPPs is of extreme significance. Therefore, many hydrologic studies have been carried out by various researchers to examine the efficiency of SbPPs and GbGPPs by comparing against RGs [29; 30; 31]. Precipitation mechanism, regional and seasonal effects of climates, basintopography, and catchment size are some other important factors affecting the accuracy of SbPPs [32; 33; 34; 35]. However, the accuracy of GbGPPs strongly relies on the reliability and the quality of the rain gauge records. Considering these facts, accuracy assessment and validation of SbPPs and GbGPPs are essential prior to decision making and many practical applications. Although, much research has been carried out to assess the hydrologic utility of SbPPs and GbGPPs in different parts of the world, up to date, few studies have yet assessed the hydrologic utility of these in the context of Thailand. According to the best understanding of the authors of this paper, only [PERSON] et al. [2], [PERSON] et al. [36], [PERSON] et al. [37], [PERSON] and [PERSON] [38], [PERSON] and [PERSON] [39], [PERSON] [40]; [PERSON] et al. [41] have evaluated the efficiency of SbPPs in Thailand. Among them, only [PERSON] et al. [2], [PERSON] et al. [36], and [PERSON] and [PERSON] [38] have examined the hydrologic utility of SbPPs for streamflow modeling in Thailand. Nevertheless, Huai Bang Sai (HBS) watershed in the north-eastern Thailand was never examined for its hydrologic utility with SbPPs and GbGPPs. Therefore, being an important watershed in Thailand in the context of agriculture and water resources, it is highly important to assess the accuracy and efficiency of different precipitation products over the HBS watershed. Therefore, this paper for the first time presents a comprehensive study to examine the effectiveness of nine SbPPs and three GbGPPs over the HBS watershed in north-eastern Thailand. The Soil & Water Assessment Tool (SWAT) was used to simulate streamflow in the HBS watershed using different precipitation products and to compare them against observed streamflow. The physically based and semi-distributed SWAT model has successfully been applied to simulate rainfall-runoff processes in many regions of the world. This model has been applied to simulate streamflow [42; 43; 44], examine land-use change effect on streamflow [45], evaluate the impact of climate change on streamflow [46], assess the water balance [47], model water qualities in streams [48], predict streamflow in ungauged catchments [49], etc. Therefore, the SWAT model holds a successful record of wide applications across the world, and its usage in the HBS watershed of Thailand is justifiable. Importantly, the north-eastern part of Thailand is world-famous for its rice production and it is also a leading exporter of rice [50]. Thailand's agriculture is heavily driven by rainfall [39]. Hence, the results of this research study will be valuable to water resources planners, agricultrists, and various stakeholders (including farmers) for decision-making purposes to obtain sustainable water usage. In addition, the study provides valuable feedback to algorithm developers to improve data retrieval algorithms of SbPPs and interpolation techniques adopted in GbGPPs in the tropical humid regions of the world.