Police have since arrested a suspect from Chantaburi province and are questioning him about the motive for the attack.
Refused entry by Khun Woothipong's secretary, the man punched the woman and entered.
Inside the office, he threw the liquid into the face of Khun Woothipong before fleeing.
Khun Woothipong was treated at Phuket International Hospital in Phuket City, where doctors said it was fortunate the liquid was bathroom cleaner rather than bleach or acid.
Chalong police are continuing their investigation.