I once asked a government official why there was so much plastic on Mae Ramphueng Beach in Rayong. He said that while the municipality put trash cans every 50 meters next to the road, Thais didn't want to walk from the beach to the road to dump their trash. The beach is not owned by the municipality but the state, so they were not allowed to put waste bins there as it "would look ugly".
By the way, people don't "recycle waste" as it requires technology, which not even the Thai government has considered investing in.