By The Nation
Relatives of Phatthisak Changpaisalkul, 36, contacted police on Tuesday night after he could not be located and a note was found.
They tracked the signal of his mobile phone and found it hanging from the handlebars of his motorcycle under the bridge over the Nan River in Moo 3 village in Tambon Tha Pho in Phitsanulok's Mueang district.
Police and divers from the Burapha Rescue Operation unit began a search for Phatthisak but the search was halted shortly after dark and it was confusing where the search should be carried out.
Maitree Krataithon, 43, a witness, told authorities that he saw a man fishing at the bridge at 10pm on Tuesday but later saw a man swimming in the river and letting himself flow downstream.
Maitree said he saw the man flow downstream for over a kilometre until he went out of sight at the curve of the river.
Maitree said he then heard dogs barking so he thought the man might get up the river's bank at the spot where dogs barked.
Rescuers decided that it was difficult to narrow down the search area so they decided to halt diving. They intend to use boats to continue the search on Thursday in case the doctor drowned and his body resurfaced downstream.