Negotiators met Hamas officials in Tehran on Oct. 26 and were given a pledge that the Thais would be released at the "right time," Areepen Uttarasin told reporters in Bangkok on Wednesday.
Israeli authorities say 1,400 people, many of them civilians, were killed and more than 230 hostages taken in the Oct. 7 attack launched by Hamas from the Gaza Strip.
In response, the Israeli military has pounded Gaza, where the Hamas-controlled health ministry says more than 8,700 Gazans have been killed.
Areepen, who led the three-person team appointed by the speaker of the Thai parliament, said they held a two-hour meeting with Hamas officials in Iran.
"I asked them to release them because they are innocent," he said.
"They assured me that they were taking good care of them, but they couldn't tell me the release date... They were waiting for the right time."
He said after the talks the Thai team -- all Muslims -- prayed with the Hamas representatives.
"They acknowledged our concerns because they know that Thailand has offered kindness and benefits to the Muslim community... They respect Thailand," Areepan said.
Thai Prime Minister Srettha Thavisin has said his government is working hard to bring the hostages home, and his foreign minister held talks in Qatar and Egypt this week.
Qatari Prime Minister Sheikh Mohammed bin Abdulrahman Al-Thani said the Gulf state was pushing ahead with efforts to free the hostages despite the "complexity" of the situation.
Srettha spoke by phone with Israeli Prime Minister Benjamin Netanyahu late Wednesday.
"He told me he would do his best to help the Thai hostages immediately," Srettha said.
Netanyahu's office said after the call that he had assured Srettha that "Israel is making every effort to free all of the hostages."
About 30,000 Thais are working in Israel, mostly in the agriculture sector, according to the kingdom's labor ministry.
Thirty two Thai nationals have been killed and 19 wounded in the conflict, and the kingdom has evacuated more than 7,000 of its citizens on repatriation flights.