Weera said authorities have tried for years to crack down on the problem of vendors exploiting wildlife, particularly in popular 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 pictures of herself playing with a herd of elephants in the street Friday night, after which she tweeted: "They all hail Empress when She walk by."
On the same night, she tweeted a few unprintable comments about what she apparently witnessed at an adult show in one of Phuket's red-light districts.
Saturday's tweets were devoted to the beach and photographs of the singer in a black bikini on a boat surrounded by turquoise water with limestone cliffs in the distance.
Before leaving Thailand on Sunday, she tweeted from the airport: "Gave the immigration guy my passport and he handed me this in return without a word. Lol." It was a picture of the singer that said "I love Rihanna."
Her next stop was Singapore before heading to Australia and New Zealand.