Vetoon Phoome's family feared the Thai farm worker had been killed by Hamas in last month's attack on Israel, until they learned on Saturday he had been free as a hostage in Gaza.
"He told me not to cry, to tell mother I’m coming back," Roongarun Wichagern told Reuters of her younger brother after an emotional reunion on a video call.
Vetoon, 33, who has been living in Israel for five years, is one of 10 Thai hostages freed by Hamas during the first truce of a seven-week-old war that started with the Palestinian terrorist group's attack.
"He said, ‘I’m not dead, I’m not dead,’" Roongarun said, calling his survival a "miracle".
The 10 Thais are among 24 hostages freed on Friday in exchange for 39 Palestinian prisoners from Israeli jails. Thailand's government said 20 of its nationals remain captive.
The freed Thai hostages will return home after 48 hours in hospital, Thailand’s foreign ministry said in a statement. Four of them had not previously been confirmed by Israel to be in captivity.
"I'm very happy to hear about the confirmation of the release of 10 Thai workers who are being treated at Shamir Medical Center in Israel under the coordinated effort of the Ministry of Foreign Affairs," Prime Minister Srettha Thavisin posted on social media.
He called for the release of the remaining "innocent Thai hostages as soon as possible".
About 30,000 Thai nationals work in Israel, forming one of its largest groups of migrant workers, many in agriculture.
Vetoon told his family he had cried out "Thailand, Thailand!" when terrorists attacked on Oct. 7, and was captured and held in tunnels, though not injured or tortured, Roongarun recounted. He was given food and water and did not appear to have lost weight, she said.
His friends believed he had died, but the family followed the news "without sleeping", hoping he had been taken hostage.
"I saw the news hostages would be released, and then someone sent a photo," Roongarun said. "It was clearly my little brother."
The released captives included the only Thai woman known to be held by Hamas, a factory worker and mother from an impoverished rural area that many leave to seek opportunities abroad.
Photographs from the Thai foreign ministry showed them meeting doctors at a medical centre in Israel.
Separate deal for Thai hostages
A source briefed on the negotiations said the release was unrelated to the truce deal with Israel and followed a separate track of talks with Hamas mediated by Egypt and Qatar.
The ministry thanked the governments of Egypt, Iran, Israel, Malaysia, Qatar and the International Committee of the Red Cross, as well as others involved in the "immense efforts" that led to the release.
Earlier reports had said about a dozen Thais had been released.
Thongkoon Onkaew told Reuters that the authorities said her son, Natthaporn Onkaew, a 26-year-old farm worker, was not among the first group released. But, she said, "I’m waiting for good news."