Netizens went into overdrive after police on Tuesday released grainy security footage of a man appearing to place a bomb-laden backpack at the crowded shrine a few minutes before the blast.
The explosion killed 20 people and injured more than 100 others in what Thailand's junta chief branded the kingdom's "worst ever" attack.
But police have not been unable to identify the apparently young man wearing a bright yellow T-shirt and glasses who left the backpack.
On social media, Thais have been using the hashtag #bombercluephoto to collate images taken in the area where the bomb exploded.
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"All camera around there before bomb. Please share and hashtag," wrote Thai Twitter user @Khemkrithera in English.
Another post, which was heavily retweeted, featured similar appeals in Thai, English, Korean and Japanese to submit any footage to police.
The area where the bomb went off was packed with office workers, tourists, shoppers and commuters, some of whom captured the moment on mobile phones and dashcams.
Netizens hope those in the vicinity at the time may have captured the suspect.
One post, written by Thai Facebook user, Sa-nguan Khumrungroj, featured an Internet search for a very similar looking T-shirt available in Indonesia.
"This shirt is sold in Indonesia," he wrote.
"I've seen this (for sale) in Pratunam," replied a friend, referring to a large clothes market in Bangkok.