The man allegedly claimed he was going to disclose the identity of a person intent on killing the couple.
Following the arrest, Pornthep Poonphon confessed he had concocted the whole story about a contract to kill "Tata" and her sweetheart Prem Busarakamwong.
"Please forgive me. I just wanted money to support my family and my ailing mother," Pornthep said with a "wai" to reporters and photographers.
The 30-year-old suspect said he gone after Tata because she appeared an easy target and clearly had a lot of money.
Pornthep, a freelance prop provider, was nabbed at around 12.30pm yesterday when he showed up at the Major Cineplex Ratchayothin to pick up Bt5 million from a woman working for Tata and Prem. He had covered his motorcycle licence plate with a false number in a bid to hide his identity.
However, police made the arrest as soon as he arrived at the meeting point. Pornthep now faces charges of attempted extortion, document forgery and forcing people to act against their will.
At a press conference, Metropolitan Police chief Lt Gen Assawin Kwanmuang said Pornthep contacted Tata and identified himself as a hitman having been approached by someone who wanted to see her and her fiance dead.
"He said he did not want to kill the couple and would be willing to disclose the identity of the mastermind if he got Bt5 million in return," Lt Gen Assawin said.
According to police, Pornthep told Tata and Prem that if he did not contact them within three days, it would mean he would have already been killed by the mastermind.
"He even advised Tata and Prem to hold a press conference about the contract killing to pre-empt any assassination attempt," Assawin said.
On February 9, Tata and Prem rushed to meet Assawin. The singer told police that she was ready to pay the money if it would ensure the safety of her and her fiance.
"After I listened to what happened, I told her that she would not have to pay the money and we planned the arrest," Assawin said.
Speaking in a separate interview at a studio, Tata thanked Assawin for his help.
"When I first heard about the threat on my life, I was so scared," the singer said.
She said people close to her did not let her know about Pornthep until February 8, when she became suspicious as to why she was barred from going out.
"The man repeatedly called my manager before that. At first, he talked about film production but finally identified himself as a professional killer. Advised by my bodyguard, my manager asked the man how he was going to kill the couple and he said he was going to use bombs," Tata said.
The pop singer said she was "relieved" Pornthep had been arrested.