The injured women, aged 40 and 61, were sent to Sancamillo Hospital for treatment. One of them suffered a neck injury, officials said.
Police were alerted to the derailment near Sa Kosi Narai station in tambon Tha Pha at 10.30am.
They found five out of 18 carriages from the Eastern & Oriental Express train had jumped the tracks. Wooden railway sleepers under the train were also broken.
Pol Sub Lt Akrit Sison, a railway police officer on board the train, said 80 foreign tourists and staff members were travelling from Singapore to the River Kwai Bridge in Kanchanaburi province when the derailment took place.
Officials believed heavy rain the day before caused soil to subside beneath the track, leading to the derailment.
The accident comes as the State Railway of Thailand (SRT) prepares to start providing accident and life insurance to railway staff and passengers.
Panthop Malakul Na Ayutthaya, director for asset management at the SRT, said accident insurance will cover healthcare costs for those injured as a result of railway accidents. It will also pay out when someone is murdered on board a train.
Life insurance will meanwhile cover funeral expenses and other necessities for the family of victims killed in train accidents.
Mr Panthop said the rape and murder of 13-year-old Nong Kaem, a passenger on an SRT train, has sparked public fear about railway services. She was attacked by an SRT worker on a night train from Surat Thani to Bangkok earlier this month.
He said the SRT must find ways to compensate the victim's family.
An SRT panel is drafting the terms of reference for firms which will join the bidding to provide insurance cover, Mr Panthop said. The draft will be handed to the SRT board for consideration next month.
The bidding could finish four months after the terms of reference are approved, he said.
"The insurance is expected to cover passengers from Jan 1. This is the SRT's New Year present to the public," Mr Panthop added.
Money spent providing insurance premiums will not affect fares for ordinary trains or free train services, but could lead to a minimal price increase on express trains, he said.
But the fee hike is yet to be calculated and would need to be approved by the SRT board.
"Although ticket prices may have to rise slightly for commercial trains, it is worthwhile because insurance will cover passengers from the time they arrive at train stations until the end of their journey," Mr Panthop said. "The insurance is expected to create confidence and draw more train passengers."
EARLIER REPORT The Eastern & Oriental Express train jumped off the track in Bang Pong district of Ratchaburi on Sunday, slightly injuring two passengers.
The luxury train with 80 passengers on board was heading towards the Bridge on the Kwai River in Kanchanaburi from Bangkok when it derailed at 10.30am as it was taking a curve before Luk Kae station, Pol Sub Lt Arkit Srisoon, an officer on the train said.
Pol Lt Chonrawee Nukongmai, a Bang Pong police officer, said the accident slightly injured two passengers who were taken to San Camillo Hospital in Bang Pong. The injured passengers were Japanese women identified only as Naami, 40, and Sumamoto, 61, he said.
Some wooden sleepers were found cracked at the scene, he added.
The passengers were all foreign tourists taking a vacation in Thailand. The train with 18 cars departed from Singapore for Thailand, travelling through Malaysia and on to Kanchanaburi, one of its stops.
State Railways of Thailand (SRT) spokeswoman Nuananong Wongchan said the injured tourists had left the hospital and rejoined the group of travellers who continued their trip by bus to their destination.
The SRT is moving six derailed cars and a locomotive back on the track and it could take at least six hours to recover the carriages before the Kanchanaburi line reopens, the SRT said on its Facebook page.
The railway agency cancelled some trains on the route including train No. 910 from Nam Tok to Thon Buri.