Police confiscated two lorises from the pair - a 20-year-old man and a 16-year-old boy - who could face charges of possession of protected animals. The charge carries a penalty of up to four years in prison and a 40,000 baht ($1535) fine.
Weera said authorities had tried for years to crack down on the problem of vendors exploiting wildlife, particularly in tourist areas where people pay to pose for pictures with elephants, orangutans and other animals.
"It's like a cat-and-mouse game. But this time it's bigger because a celebrity like Rihanna posted the picture, and there were more than 200,000 'likes' from around the world," he said.
Rihanna also posted a picture of herself playing with a herd of elephants in the street on Friday night, with the comment: "They all hail Empress when She walk by."
Before leaving Thailand on Sunday, she posted from the airport: "Gave the immigration guy my passport and he h anded me this in return without a word. Lol." The image had a picture of the singer that said "I love Rihanna".
She performed on Sunday in Singapore before her tour heads to Australia and New Zealand.
- AP