Pride of India, Banaba, Queen's crape myrtle (Lagerstroemia speciosa).

Lagerstremia speciosao is a species of Lagerstroemia native to tropical southern Asia. This plant is grown along streets in Vietnam which is called 'Bằng Lăng tim". It is widely cultivated as an ornamental plant in tropical and subtropical areas, especially in South East Asia, India and the Philippines.

If you want more information about this flower, just search the plant's Latin name on Google: