The tourism industry in Thailand accounts for approximately 10% of its GDP, and thus quite important for Thailand. In spite of the recent tension caused by domestic political issues, the tourism industry had been stable. For instance, after the political turmoil of last year, the industry saw a decrease by about 6%, 2.8 million tourists visited Thailand again only during January 2015. Hence it is predicted that the sightseeing industry has been affected by the terrorist attack, but will not last long.
In the meantime, the Ministry of Tourism and Sports and the travel association have recently made some promotion, one of which is to target Chinese and released on 2nd September, in order to reduce anxieties among potential foreign tourists. They seem to highlight other destination such as Chiang Mai, Phuket and Sukhothai, while excluding Bangkok. Thanks to these promotional efforts, 200,000 Chinese are anticipated to visit Thailand during their national holiday.
After the attack, security has been tightened not only in Bangkok but also the aforementioned places. Hence I still confidentially recommend you to visit Thailand.