Near Khao San Road, just before we walked over to Wat Bowon, I met a young lady from California. She was either in university, or had just finished. After talking with her for a few minutes and answering some questions she had about Bangkok, she walked with us over to Wat Bowon. And like a lot of tourists, especially backpackers focused on getting to an exotic island or beach, she was dressed in a short skirt and revealing tank top. And, of course, when we reached the temple, there were signs stating that appropriate attire - for women, pants or a long skirt or dress - had to be worn inside the temple. I had to point this out to this young American lady. Luckily for her, the door to the ordination hall was open, and she still got a very good view of the murals and Buddhas. To make sure that the rules were followed, there was a an older Thai woman who walked around the temple reminding people of the dress code. She would smile and say, "Respect" in English. Thais wouldn't need to be reminded!
Wat Bowonniwet Vihara is among the most important Buddhist temples, or wats, in Thailand. It stands in the Bangkok district of Phra Nakhon, and is an important center for Thai Theravada Buddhism, in particular the school of Thammayut Nikaya. The temple has a long history of patronage by the Chakri dynasty, the current royal house of the country. It has served as a major temple for many years. - source
For a more detailed history and description of Wat Bowon, click here.