Rachan Teerakijnukul, 50, allegedly confessed to throwing chemicals on passersby who he thought looked down on him, MCOT reported Monday.
Rachan carried out the attacks in several areas of Bangkok, including Saphan Khwai, Pratunam, Ratchaprasong, Victory Monument, and Lat Phrao.
He also admitted to being addicted to crystal meth, Acting Metropolitan Police Bureau Chief Kamronwit Thoopkrachang said.
Rachan was arrested in his home Sunday. Police also seized a tricycle cart he used to collect scraps and bathroom cleanser bottles, which he allegedly used against the victims.