Bangkok bomber ?is part of network? The bomb attack that killed 20 people at Bangkok's Erawan shrine on Monday was carried out by a "network", Thailand's chief of police has said.Police have released a sketch of the main suspect, a man in a yellow T-shirt who was filmed by security cameras leaving a backpack at the shrine.Police later said two other people seen on CCTV were being treated as suspects.Prime Minister Prayuth Chan-ocha has described the incident as the worst-ever attack on Thailand.