Khunying Laohaphan said: "With the resilience of the Thai society, you can be assured that Thailand will emerge as a stronger and more vibrant democracy. We will ensure a swift return to democracy with a definite timeline."
An interim constitution, to be put in place in the next few days, would ensure full civil liberties and human rights, she said, adding that a new civilian government would also be in place "within the coming days".
"We can well expect that one of the first tasks of the new civilian government will be to do away with martial law. Constitutional reform will lead to a new constitution and general elections within one year if not sooner.
"I wish to also assure the General Assembly that Thailand's foreign policy will remain unchanged."
She said that her country would continue to be guided by the UN Charter and remained committed to all its obligations under international treaties.
Thaksin Shinawatra, the prime minister, was ousted from power by Thai military leaders on September 19 while he was in New York attending the annual opening debate of the new General Assembly session. Laohaphan also served as UN ambassador under Thaksin.
Thaksin had been scheduled to address the assembly last week but left New York for London after learning he was no longer Thailand's leader.