
Police Special Branch pointed out Thursday that the use of the national flag in such a way was a breach of the National Flag Act 1979, and punishable by up to a year in jail and/or Bt2,000 in fines.
Members of the Thai branch of the Manchester City supporters club displayed the offending banner yesterday at Suvarnabhumi airport to welcome the club's manager, Sven Goran Erickson.
Police Special Branch deputy commissioner MajorGen Trithosa Ronnaritthiwichai said the banner breached Article 53 of the bill, which outlaws the placing of letters, numbers or symbols on the national flag.
He said police would issue a warning to the violators and that they would be arrested if they continued to use the flag on their banner.
Erickson, the former England manager, is visiting Thailand to sign three Thai players to join the Premiership club.