Bangkok United defeated Lamphun Warriors 2-0 on Sunday night to trim Thai League 1 leaders Buriram United's advantage to four points.
In a one-sided match, Brazilian striker Heberty Fernandes opened the scoring for the Angels after 51 minutes and Ratchanart Arunyapairoj added the other goal in the 73rd minute.
After 12 games, the capital side have 26 points while the Thunder Castle are on 30 points.
Promoted club Lamphun are last with six points.
"It was an important game for us as we needed a win after losing [to Buriram] last week," said Bangkok United coach Aurelio Vidmar.
"We should have scored more goals. The season is still long and we must stay close to the leaders.
"For the second leg [of the season], I think we don't have to make changes as our [new] foreign players have settled in now."
In the weekend's last match, Ratchaburi drew 1-1 with Port.
