Satellite Based Augmentation System (SBAS) provides correction message services as an additional system to navigation satellites.
Several SBAS services exist in many regions and usually cover a large area. Although, Thailand is not geographically located within
a center of SBAS service coverage, users in Thailand can still receive correction messages from some available systems. This study
aims to evaluate the GNSS positioning accuracy with corrections from different operational SBAS systems; namely, SPAN, GAGAN
and BDSBAS when its positioning strategy is Single Point Positioning (SPP). The positioning results are then compared with solutions
from Precise Point Positioning (PPP) which are referred to as reference coordinates. GNSS observations in this study are taken from
40 GNSS Continuously Operating Reference Stations (CORS) operated by the Royal Thai Survey Department. Certain period
observations; comprising of September 2019, December 2019, and April 2020, are selected into computations. This research shows
that three SBASs could not significantly improve both horizontal and vertical positioning accuracy comparing with GPS Single Point
Positioning solutions.