Metrication in the United States traditional mile-based lengths. In the Olympics, athletes run 1500 meters, not 1600 meters. Running races in the U.S. are usually run in metric distances (e.g., the 100 metres dash or the 5K run), although the mile distance remains popular. But even 5 and 10 kilometer races most often have mile markers on the course, and no kilometer markers. Long-distance races are often measured in kilometers, although exceptions exist (generally 10 mile races). The marathon is referred to as a 26.219-mile race (the official marathon standard distance originally being in English units — 26 miles, 385 yards) rather than 42.195 km.
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