The offending advert, called Luem Aeb (meaning 'forget to deceive'), was broadcast on Bangkok's sky train system from December 28 to January 13 and on YouTube.
'The MTF transgender/transwomen character is openly mocked as being "deceitful",' read the open letter to IKEA from Thai Transgender Alliance.
'The transgender content of the advertisement is negative and stereo-typical in nature, perpetuating misunderstanding transgenderism as human sexuality for "deceitful and deviant lifestyle".'
The advert shows a woman who is so surprised by a sale item that she speaks with a male voice. The man she is with looks shocked and horrified. The last scene of the advert shows the man running away as the woman carries a box of flat-packed furniture by herself.
The letter from Thai Transgender Alliance demands that IKEA Global issue an official public statement about the advert.