A man believed to be high on drugs was hauled from a muddy canal in Pathum Thani and arrested on Tuesday night after earlier kidnapping a boy and threatening to stab him and a motorcycle taxi driver.

Thanongsak Chuanchom appeared confused, telling arresting officers he just "wanted a motorcycle to take me back to my girlfriend" who had left him three days ago, Manager Online News reported on Wednesday.

The 27-year-old worker, based in Min Buri, eastern Bangkok, also claimed he also had no idea why he was in Pathum Thani but allegedly admitted he had been drinking alcohol and had taken crystal methamphetamine earlier in the evening.

According to police, Mr Thanongsak was walking along Soi Uttsaha in Pathum Thani's Thanyaburi district, when he saw the boy. He went up to him, put a knife point to his throat and ordered him to stay calm. The suspect then hailed a passing motorcycle taxi and told the rider to take them to Future Park Rangsit shopping complex.

The driver, Mongkhon Kingkasem, told police that the man threatened to stab him and the boy if he did not speed up. That was when he became aware the man had a weapon.

Minutes later, as they were passing a factory, Mr Mongkhon decided to stop the bike, ran over to a security guard and asked for help. The driver of a passing car also pulled over and got out of his vehicle in order to try and help the boy.

Motorist Phanan Krutsamphan, 43, told police that the knife-wielding passenger warned them not to come closer.

"Fortunately the boy shook the man off and fled," Mr Phanan recalled. The man then suddenly jumped into the canal in an attempt to flee.

Police and rescuers were called to the area and the suspect was apprehended about 40 minutes later. A Rangsit municipality boat cornered him in the muddy canal and rescuers then grabbed him and hauled him up onto the bank.

Mr Thanongsak continued to resist arrest and was forcibly carried to a car.

"We've charged the suspect on five counts," Pratunam Chulalongkorn police chief Pannaphat Detchotphisit said later. These included including using a weapon to steal an asset and detaining and assaulting the boy.

He also tested positive for drug use for which he would face additional charge, Pol Col Pannaphat said.

Police said Mr Thanongsak was wanted on an arrest warrant issued by Chai Nat Provincial Court in 2014 for illegal possession of a firearm.