"I saw Asian shemale erect a new billboard." (Using 'erect' as a verb).
If you are asking about the grammatically correct article to use before the phrase "Asian shemale erect," the proper article is . asian shemale erect
Note: If the phrase is being used as a specific title or descriptor, the choice of article follows the same phonetic rule. "I saw Asian shemale erect a new billboard
The choice between "a" and "an" depends on the sound of the following word: asian shemale erect