At the beginning of the trailer, the disclaimer clarifies that it is a fan-made trailer. So, Mr. Khan is not playing the role of Tipu.
The alleged trailer titled 'Tipu Sultan Trailer Shah Rukh Khan New movie' was uploaded on September 20, 2018. The disclaimer mentions that it has edited clips from various videos on Youtube. This is a fanmade trailer that is in no way related to the actor and he is not filming the movie on Tipu Sultan.