Thai Buddhist hard-liners have filed a police complaint against a young female artist over paintings that depict Buddha as the 1960s Japanese superhero Ultraman.

The complaint over four paintings, displayed last week at a shopping mall in northeastern Thailand, highlights the emboldenment of ultraconservative Buddhist groups that seek to go further than establishment religious authorities in combating perceived threats to their faith.

Buddhism, followed by more than 90 percent of Thais, is one of three traditional pillars of Thai society, alongside the nation and the monarchy.