The attack took place in Bangkok’s Laksi district, close to the Don Muang airport.
Ten people have died and at least 577 have been wounded in politically related violence in Thailand since November.
State of emergency
Last week a Thai anti-government protest leader was shot and killed in Bangkok as violence erupted in demonstrations aimed at preventing early voting ahead of a disputed election next week.
The government announced a state of emergency late in the wake of a string of attacks that have mostly been aimed at demonstrators protesting peacefully in Bangkok.
Protesters are calling for Yingluck Shinawatra, the Thai prime minister, to step down. She is accused of being a proxy for her brother, ousted former premier Thaksin Shinawatra.
Ms Yingluck called a national election for 2 February, one she is expected to win because of a large rural support base. However, the largely middle class and royalist supporting protesters are opposed to this.
Early voting was due to take place in 50 polling stations across the Thai capital on Sunday, but 45 of these were closed due to protests.