Police have seized a speedboat belonging to a prime suspect in the murder of a German property broker, as they believe he might have planned to use it to dump the victim’s body at sea.

Police took the 18-foot speedboat from a house on Phra Tamnak Soi 5 in Pattaya on Wednesday night.

The boat was owned by Olaf Thorsten Brinkmann, 52, one of four suspects in the murder of Hans Peter Mack, 62. The boat was kept at the house of a German friend who alerted police after learning about the arrest of his compatriot, said a police source.

His friend told investigators that Mr Brinkmann had sought help on July 8 to tow his speedboat from Nong Krabok Soi 4 to the Chokchai Garden Home housing estate in Nong Prue.

On July 9, the friend told Mr Brinkmann that he would tow the boat to the Ocean Marina pier in Pattaya. But because it had no registration documents, the boat could not be moored there. He then brought the boat to Phra Tamnak Soi 5.

Surveillance video at a fishing supplies shop showed Mr Brinkmann and another suspect, Shahrukh Karim Uddin, buying some gear at the shop. Mr Uddin, 27, a Pakistani with Thai nationality, was arrested in Kanchanaburi on Wednesday afternoon after trying to flee across the border to Myanmar.

Police believe the two men were planning to go to sea and dump Mack’s body overboard. However, the dismembered body of the victim was found hidden in a freezer at a rented house on Monday night — six days after the German man went missing.