Pol Maj-Gen Suebsak Pansuri, commander of the Metropolitan Police Division 5, said the two arrested suspects were attached to Thong Lor police station. They were named as Pol Sgt Maj Phuripat Chuenjumpa and Pol Sen Sgt Maj Sathit Chantrasom.
Still at large are two officers attached to Lumpini police station: Pol Lt Akaranet Mutawan and Pol Lt Virat Intrayod.
Pol Maj-Gen Suebsak said all four officers were dismissed from the force.
Pol Maj Gen Prinya Chansuriya, deputy chief of the Metropolitan Police Bureau, said the four suspects worked with an Uzbek man identified as Muhiddin Sharipov, who remained at large.
Officers said the gang confronted two Italian men at an ATM in Bangkok's Nana area on Monday and accused of them of using a fake card to withdraw cash at an ATM.
The two Italian engineers - Danilo Der Vito, 51, and Antonio Di Muro, 62 - had arrived in Thailand just hours earlier to start a vacation.
Pol Lt Col Chaiya Kongsap, chief of Lumpini police station, said the suspects demanded 2 million baht from the tourists in exchange of not filing charges.
The victims negotiated a payment of 25,000 euros (1 million baht), said Pol Lt Col Chaiya. They were then taken to a hotel room on Sukhumvit Soi 57 and held there.
He said the suspects on Tuesday forced the victims to phone their relatives in Italy and ask for the money to be transferred. The Italians took that opportunity to tell their relatives about the ransom.
The relatives then notified Italian authorities who in turn informed the Italian Embassy in Thailand, which contacted Thai police, said Pol Lt Col Chaiya said.
Police managed to free the captives but the kidnappers fled before officers arrived, he said.
Pol Maj Gen Suebsak said the Criminal Court of Southern Bangkok had issued arrest warrants for Pol Lt Akaranet and Pol Lt Virat. All the suspects will be charged with robbery and detention for ransom.