An alleged accomplice in the murder of a Thai couple in Taiwan was arrested on Sunday afternoon, a police source said.

Thanawat Poomkhemthong was detained by police at a house in Kalasin province.

Earier on Sunday, a police source said the Criminal Court had issued warrants for the arrests of Mr Thanawat and another alleged accomplice, Samart Sae Lee.

The arrest warrants for Mr Samart and Mr Thanawat were sought after Santi Supa-apiradeepailin, the prime suspect, surrendered to police in Chiang Mai's Chiang Dao district on Friday.

Mr Santi was immediately taken to Bangkok.

During questioning, Mr Santi denied killing Prasert Norat, 32, and his 35-year-old wife Potjanee, who was five months pregnant with twins, claiming it was the work of a Taiwanese mafia gang. Police continued interrogating him overnight.

On Saturday, police said Mr Santi reversed his statement and confessed that it was he and two other Thai nationals - Mr Samart and Mr Thanawat - who killed Prasert and Pojanee in Taiwan over a drug business conflict, and that the two suspects returned to Thailand on June 11.

The bodies of Prasert and Potjanee were found in their car parked outside a rail station near Taipei on June 12.

Mr Santi was seen in security camera footage when the three had an appointment on June 8. He drove their BMW to the train station in the early morning of June 9.

He flew to Thailand later on June 9, landing at Suvarnabhumi airport and immediately went to Chiang Mai. He was charged with premeditated murder.