Marathon world record progression races were first held in 1896, but the distance was not standardized by the International Association of Athletics Federations (IAAF) until 1921. The actual distance for pre-1921 races frequently varied slightly from the present figure of 42.195 km (26 miles 385 yards). In qualifying races for the 1896 Summer Olympics, Greek runners Charilaos Vasilakos (3:18:00) and Ioannis Lavrentis (3:11:27) won the first two modern marathons. On April 10, 1896, Spiridon Louis of Greece won the first Olympic marathon in Athens, Greece in a time of 2:58:50; however, the distance for the event was reported to be only 40,000 meters. Three
Bangkok Marathon course passes many historical landmarks of cultural and ethnic importance. The marathon starts and finishes in front of The Royal Grand Palace at Sanam Chai Road. The race course is sanctioned by The Association of International Marathons and Distance Races (AIMS) and the Amateur Athletic Association of Thailand (IAAF Rules). In 2013, the course of the half marathon was changed at the last minute because of concurrent Bangkok street protests which reduced the distance of the half marathon from 21.1 km (13.1 miles) to 19.7 km (12.2 miles). In 2015, the half marathon was accidentally extended from 21.1 km (13.1