The restriction on taking photos of the Mae Nak Shrine with “professional cameras” is likely due to cultural or religious beliefs and practices. In Thai culture, there is a deep respect and reverence for sacred sites and religious objects. The Mae Nak Shrine is considered to be a sacred place where people come to pay their respects and make offerings. Prohibiting photography in such areas helps maintain the sanctity and spiritual atmosphere of the shrine. Additionally, it may also be a way to ensure the privacy and respect for those who come to worship or seek blessings at the shrine. It’s important to follow local customs and guidelines when visiting Wat Mahabut to honor and appreciate the local traditions. With that being said, you are allowed to take smartphone photos of the shrine.