But despite the stress, Gen Yuthasak says he has not wavered in pursuing his work at the ministry.
"I concede that I was under a huge amount of stress at the beginning because I had no idea what was happening," Gen Yuthasak told the Bangkok Post, referring to the clip that surfaced on YouTube on July 6.
A discussion on the recording centred on pushing for an amnesty bill and taking control of the armed forces.
Critics believed the recording was made shortly before Gen Yuthasak was made deputy defence minister in the cabinet reshuffle on June 30.
The minister appeared stressed after the clip emerged and refused several media interview requests.
"I need to be patient and strong as many people have given me encouragement," Gen Yuthasak said. "For me, the issue is trivial compared to the harsh things I had previously encountered in my life".
"It is suspicious because I assumed the post of deputy defence minister on July 5 and the clip was released on July 6."
The deputy minister, however, refused to concede whether the clip was real. No witnesses have come forward and no proof of its authenticity has surfaced.
"There is nothing happening in line with the clip now," Gen Yuthasak said.
He was referring to the discussion heard on the clip supporting the tabling of the amnesty bill at the Defence Council, a move he said is a misstep concerning present regulations. No talks have been made to help Thaksin, he said.
"I do not know how this clip came about, but for sure it was doctored," Gen Yuthasak said. "The politics [surrounding the clip] are so dirty."
The deputy minister revealed there have been continued attempts to oust him from his ministerial post.
He said the person who spread the news about the clip "wants to replace me as the deputy defence minister".
"I haven't thought about resigning now because I still have a lot of work to do," the deputy minister said.
Prime Minister and Defence Minister Yingluck Shinawatra had instructed him to screen all the ministry's work.
"For the military reshuffle, I helped supply information on the candidates and prepared their records to compare," he said. He stressed the clip has not harmed his relations with the military leadership.
"I have known Supreme Commander Tanasak Patimapragorn and army chief Prayuth Chan-ocha for a long time," Gen Yuthasak said. "The matter is trivial and no one paid attention to it."
Gen Yuthasak confirmed he is still beloved by the armed forces leaders, particularly Gen Prayuth, who has always given him support and has warned him about many issues.
He said he will decide to step down when the timing is right. He is now 77.
"I have worked for the defence ministry for 19 years, so no one can play tricks on me," he said. "I am still capable of taking care of issues for the premier and minister."
Gen Yuthasak added he has been assigned by the premier to organise two significant events: overseeing the international fireworks display to celebrate His Majesty the King's birthday on Dec 5 in Prachuap Khiri Khan's Hua Hin district, and the marching band competition of worldwide armed forces in honour of the King.