But Thailand will have to wait for at least another two years to claim the women's 100m title as their runners could only take silver and bronze.
At Wunna Theikhdi Stadium, Jirapong, from Surat Thani, crossed the finish line in 10.48sec, ahead of Indonesia's Isawandi (10.51) and Muhammad Jamal of Singapore (10.55).
"I am really happy although my time was much slower than my personal best of 10.35," said Jirapong, who became Thailand's first 100m winner since Watchara Sondee in 2005.
"I was in lane five and was sandwiched by Indonesian runners in lane four and lane six. That made me feel uncomfortable but I managed to win."
In his first SEA Games, the 20-year-old Thai, who only started running the distance three years ago, will also compete in the men's 200m.
With his success in Myanmar, he now eyes a top-three finish in the 100m at the 2014 Asian Games in Incheon, South Korea.
In the women's 100m, Vietnam's Thi Huong Vu claimed gold in 11.59sec, comfortably beating Thais Neeranuch Klomdee (11.85) and Tassaporn Wannakit (11.91).
Neeranuch, the last Thai to win the event in 2003, said the 27-year-old Vietnamese, who won silver at the 2010 Asian Games, had been one of the continent's top sprinters in the past few years.
"She is a great runner and deserves the win," Neeranuch said.
The 33-year-old veteran has represented Thailand for 16 years and this will be her last SEA Games. She aims to take part in next year's Asian Games before retiring.
Wassana Winatho claimed her second gold of the Myanmar Games with her win in the women's 400m hurdles. She crossed the line in 58.85sec to defeat Vietnam's Thi Lan Quach (58.93) and Singapore's Dipna Lim Prasad (59.96).
Wassana, who had won gold in the heptathlon, said she was unsure if she would be fit for today's long jump because of back pain.
In the men's javelin throw, Peerchet Jantra took home the title with a Games record of 76.30m, ahead of compatriot Hussadin Rodmanee, who managed 75.46m.
Distance running specialist Boonthung Srisung won silver in the men's 5000m. He clocked 14.21min behind gold medallists Van Lai Nguyen of Vietnam who crossed the line in 14.19min.
bangkokposts.com
