A suspected kidnapper has been arrested when a collision he was involved in enabled a Chinese woman to escape - after she was allegedly drugged and hogtied on the backseat.

Chinese national Zhao Wulin, 36, was driving along the Si Rat Expressway in Bangkok, Thailand, when he rear-ended Thai driver Sompong Seesod's Toyota Fortuner on September 14.

Using Google Translate, Zhao told Sompong that he would pay for the damages using cash, but the Thai man insisted they both contact their insurance companies instead.

But while waiting for the representatives to arrive, Sompong said he was shocked when officers from Expressway Police Station 2 converged at the scene and suddenly cuffed Zhao.

Sompong said: 'I later learned from the police that while I was sitting in my car calling the insurance company, a young Chinese woman ran down from Zhao Wulin's Toyota Yaris sedan before waving to another vehicle on the expressway for help.

'I was surprised because I did not think that Mr Zhao was acting suspiciously and I didn't notice a Chinese woman inside the car.'

Police later revealed that during the chaos, a Chinese woman, 27, who was tied with rope in Zhao's Toyota Yaris had managed to free herself and call for help from a passing taxi.

Noppasin Poonsawat, deputy commissioner of the Metropolitan Police, told local media that the lady had been working as an agent in China assisting local women with plastic surgery arrangements in South Korea, while Zhao from Henan province held a work permit for foreigners in Cambodia.

The pair were on holiday in Thailand and had been speaking for 10 days through messaging app Telegram before agreeing to meet for dinner at a restaurant in Bangkok's Ramkhamhaeng area on September 13.

The woman claimed she had begun to feel dizzy after drinking alcohol, then woke up the following day in Zhao's hotel room in the Lat Phrao district.

Zhao reportedly convinced her to take a trip to the coastal city Pattaya, but while on the road, he allegedly threatened her to fork over 50,000 Chinese yuan (6,870 USD).

The woman said she had to call a friend to borrow money.

The expressway crash occurred when Zhao was taking the girl to the bank to withdraw, allowing her to run away.

Deputy Commissioner Noppasin said police have seized from Zhao 100,000 THB in cash and other currencies, and the rope with which he tied the woman.

Zhao has been charged with extortion, detention, obscenity, and 'impeding freedom.'

Police said they were investigating if Zhao was acting alone or connected to extortion gangs.

It comes as Thailand struggles to balance welcoming Chinese tourists, who boost the economy, while also trying to control the large criminal element from the Communist mainland, that infiltrates its neighbouring countries where police are more malleable.

New Prime Minister Srettha Thavisin has rolled out visa-exempt entry from China but officials fear the measures could be abused.