The protesters were injured in two shootouts occurred at a rally site and nearby place at an intersection near the Khao San Road.
The seven were security guards for the anti-government movement People's Democratic Reform Committee led by the opposition, police said.
A photo journalist narrowly escaped as a bullet grazed his leg.
Thailand is in the grip of a political crisis with opposition Democrat Party backed protesters demanding Prime minister Yingluck to step down.
Eight people, including a policeman, have been killed and several injured in street protests in Bangkok in the past several weeks.
The Indian Embassy in Bangkok has advised all Indian nationals residing here and tourists to stay away from protest areas.
Protesters have called for a total shutdown on January 13 to pressurise Yingluck to step down. Some believe ousted former leader Thaksin Shinawatra -- Yingluck's brother -- is still controlling events in Thailand through his sister and her government.
