A controversial Chinese-language billboard advertising passport and citizenship application services was removed on Monday.
The giant Chinese advert raised concerns over the entry of undesirable visitors who avoid proper checks and are involved in criminal activity.
Prime Minister Srettha Thavisin ordered police to investigate the advertisement and possible illicit business activity in Huai Khwang, an area with a lot of Chinese investment.
This followed a social media post about a Chinese-language billboard in Huai Khwang district, Bangkok.
The Chinese-language advertisement offered quick passport and citizenship services. It claimed to arrange new citizenship in just 30 days.
The billboard showed pictures of Indonesian, Cambodian, Turkish and Vanuatuan passports.
Officials suspect the advertised service is linked to passport forgery or other fraud.
The advertisement was removed about 10am on Monday.
