Dogs and other animals are not allowed on the pitch, the Thai Premier League said.
A dog ran onto the pitch during a TPL match between hosts Chonburi and Buriram United last week, and the uninvited guest was taken away.
The TPL did not slap a fine on Chonburi as the dog did not disrupt the game and players maintained their concentration on the ball.
The league sent a warning letter to the Sharks reminding them that dogs must not be allowed on the pitch.
The visitors beat the hosts 3-1 on that day.
Dogs are not strangers to football fans and players.
Last month, Si Sa Ket were fined 10,000 baht by the TPL for allowing a dog on the field during a match against Nakhon Ratchasima.
Meanwhile, TPL side Osotspa have appointed former Thailand international Kritsada Piendit as their new head coach, replacing Brazilian Stefano Cugurra Teco.
Teco was sacked recently following a series of poor results.
Osotspa are currently 10th in the 18-team league.
Meanwhile, Fifa has dismissed claims by Indonesia that it will send officials to Jakarta in October with a view to overturning the ban on the Southeast Asian nation for government interference.
Indonesian Youth and Sports Minister Imam Nahrawi said last week Fifa would send an investigative team and see that all was well again in the country's soccer governance, but the world governing body told Reuters the trip was news to them.
"Fifa and AFC [Asian Football Confederation] would like to confirm that no such visit is planned," a spokesman said.
"Nor will a Fifa/AFC mission take place until the respective governmental authorities have duly respected the principle of autonomy of sports organisations."
Fifa banned Indonesia in June after the government refused to back down in their demands that the local football association (PSSI) block two clubs from taking part in the top flight domestic league because of concerns about their ownership.
The PSSI stood firm but the league was halted after two rounds and eventually cancelled after the government stepped in.
Attempts to restart the Super League have failed.
The Fifa suspension led to Indonesia, one of Asia's biggest soccer markets, being kicked out of the 2018 World Cup qualifying campaign.