A photo of the incident, which was shared on Chinese social media recently, showed the couple standing by and waiting for their daughter as she urinates in front of the Grand Palace, South China Morning Post reported.
The photo has gone viral with over 1,400 shares and 700 comments.
A tourist who took the photo said the family was from China, according to Thailand’s Morning News TV3.
Tourism and Sports Minister Sermsak Pongpanit criticized the incident and described the behavior of the tourists as "inappropriate," the Bangkok Post reported, adding he has ordered relevant agencies to investigate.
Located in the heart of Bangkok, The Grand Palace is considered as the symbol of Thailand and Thai royal family. Now, the place is used for hosting royal ceremonies and welcoming the king's guests, state guests, and other foreign dignitaries.
Many netizens criticized the Chinese couple for disrespecting Thai culture on social media.
One user wrote "Where were the officers... why did they allow this incident to happen?"
"They should be punished for insulting the monarchy," another wrote.
The Thai royal family is highly respected by Thai people and royal insult could be punished by imprisonment of between three and 15 years.
Last year, a photo of two foreign women sunbathing in bikini costumes at Sanam Luang, a public square in front of the Grand Palace, also triggered a wave of outcry from Thais.