Officers are now looking for a second man, recorded by a security camera helping alleged killer Prasit Navee, 47, to carry and dump the body of his brother Chayadal, 43, early on Thursday morning.
Khun Prasit originally told police that his brother, who suffered from a mental disorder, may have suffered some kind of fit associated with possession by a spirit.
Khun Prasit later admitted to kicking his brother in the head as his brother continued to pray in the family home while he was trying to sleep, police said.
There were signs of the floor being cleaned that indicated to police that Khun Prasit's original version of what transpired may not have been the truth.
The body was found in a garden patch near Villa California Village, not far from the landmark Rolly Tasker Sail factory in Phuket's Chao Fa Road West.