Lak Song (Thai: หลักสอง, pronounced [làk sɔ̌ːŋ]) is a khwaeng (subdistrict) of Bang Khae district, Bangkok's Thonburi side.

Originally, Lak Song was a part of amphoe (district) Nong Khaem, a westernmost of Bangkok.

Until 1998, the Ministry of Interior has merged certain areas of Nong Khaem and Phasi Charoen with Bang Khae, which is a newly established district.

It is a canal dug during King Mongkut (Rama IV)'s reign linking Bangkok to Krathum Baen of Samut Sakhon province.

[4] Lak Song has a total area of 9.25 km2 (3.57 mi2),[5] regarded as the south-west part of the district.