Prime Minister Prayuth Chan-ocha on Monday called on Thais to be the "eyes and ears" of security forces in order to boost international confidence in Thailand after the second explosion in the capital Bangkok in just over a month.

Police have detained three people in connection with the grenade explosion on Saturday night outside Bangkok's Ratchadaphisek Criminal Court. No one was hurt in the attack.

"We ask the public to be the eyes and ears of authorities because security must come first. We must rebuild confidence for foreigners," Prayuth told reporters. 

Thailand remains under martial law and military leaders say they have no plans to lift it. The law has kept away some visitors, as they are unable to buy travel insurance for countries under martial law.

Thailand has been under martial law since the military seized power on May 22 last year to end months of sometimes deadly street protests.

Chief of Royal Thai Police General Somyot Poompanmuang said those behind Saturday's attack were from "the same political background" as those responsible for the twin explosions outside Bangkok's Siam Paragon shopping mall last month.

Somyot told reporters that arrest warrants had been issued for five people, including the three suspects in police custody. He added that, under martial law, the suspects can be detained for up to seven days and then released unless charged.

One of the suspects, Mahahin Khunthong, told reporters on Sunday that he and another man were paid 20,000 baht ($614) to carry out the attack and that other attacks were planned in order to "prompt United Nations intervention."

Political gatherings are banned under martial law, but that has not stopped some university students from staging protests against the ruling junta, known as the National Council for Peace and Order (NCPO). The NCPO has justified martial law by saying security in Thailand is unstable, citing certain groups' opposition to military rule.

(Reuters)