The prime minister made the remark in connection to the death of two Britons in the country.
The duo in their mid-20s, David Miller and Hannah Witheridge, were found murdered earlier this week after they went to a beach party in Koh Tao island in the Gulf of Thailand. No arrests have been made in the case so far.
Speaking in a live broadcast on Wednesday, PM Chan-ocha said: "There are always problems with tourist safety. They think our country is beautiful and is safe so they can do whatever they want, they can wear bikinis and walk everywhere," according to the AFP news agency.
The prime minister asked whether the tourists would be safe in bikinis, unless they are not beautiful.
Chan-ocha later apologized for his comment after it led to a controversy. Even the British embassy contacted the Thai prime minister to seek clarification over the remark.