BANGKOK, Aug. 11 (Xinhua) -- More than 4,000 bicyclists joined in a cycling activity on Saturday as part of the celebrations of Thailand's Her Majesty Queen Mother Sirikit's 86th birthday anniversary in a southern Thai province.

The cycling event in Pak Phanang district of Nakhon Si Thammarat, about 790 km south of Bangkok, was organized one day ahead of Her Majesty the Queen Mother's birthday anniversary which falls on Aug. 12.

The activity was organized by Nakhon Arsa Foundation, the Department of Communicable Disease Control and the host Pak Phanang district.

The 25-kilometer-long route for the 4,000-plus bicyclists, mostly clad in blue T-shirts, went on a round trip from Pak Phanang watergate, passing Pak Phanang River bridge, the district's beach area and the 100-Year-Old Market and finally returning to the starting point.?