For Harley Davidson service in Khon Kaen try Silver Star Bike Shop.
https://www.gt-rider.com/thailand-motorcycle-forum/showthread.php/38734-Silver-Star-Harley-Davidson-Service-Khon-Kaen
https://www.gt-rider.com/thailand-motorcycle-forum/showthread.php/38734-Silver-Star-Harley-Davidson-Service-Khon-Kaen