The hosts were in complete control of the Group A clash from the outset at the Rajamangala National Stadium in Bangkok and put on a show to delight their home fans.
However, with the visitors standing resilient, patience proved crucial as it took until just before half-time before Thailand took the lead through Yotsakorn Burapha.
The goal clearly boosted the hosts and the floodgates opened in the second-half, with Yotsakorn scoring in the 71st and 72nd minutes to complete his hat-trick, before further goals from Siraphop Wandee, Iklas Sanron and Kakana Khamyok cemented the win.
Timor-Leste managed an injury time consolation goal from Palamito Caffin but it proved immaterial as the hosts got off to the start that coach Thawatchai Damrong-Ongtrakul had demanded.
Thawatchai told a pre-match press conference that the only target for the team is to reclaim the gold medal.
“Our aim is very clear - we want to win the gold medal,” said Thawatchai. “Thailand have not won football gold at the SEA Games for quite some time.
“Now that we are hosts, we have prepared extensively over the past months. We trained together through the Asean Championship in Indonesia, the Asian Championship qualifiers in Thailand, warm-up matches in China, and most recently against India.
“From four training camps, we selected what we believe is the strongest squad to represent the nation.”
“The SEA Games is the biggest sporting event in South-east Asia. We want to bring back the title and restore faith in Thai football across the region. Hosting the Games after many years is a special opportunity and we want to make our fans proud.”
The tournament kicked off earlier Wednesday with Vietnam beating Laos 2-1.
Thailand’s next match is against Singapore on Dec 11.