The Thai wedding ceremony is unique. It used to be more complex with lots of steps.
First, we will have a Monk Blessing as is the Buddhism custom at the house of the bride or the bridegroom (which will be the place for the event) in the morning. After that, there will be marriage registration. Then, we have lunch together. Many couples do not have this part of the day of the monk blessing and registration at home. They may go to register at the county office the day before or after the wedding.
In the afternoon, the traditional wedding customs will be followed. It is called ROD-NAM-SANG, and is the main event where both the bride and the bridegroom's family get together. They witness this important event. Both the bridge and the bridegroom will sit close together on the floor (or small stage) with their hands held in WAI style (like the way we pay respect to the Lord Buddha). A flower chain connects the hands. The most senior person will act as the leader of the event. He or she will start to soak the couple's hands in water and wish them good luck. The water is contained in a conch shell container (ROD is soak, NAM is water, and SANG is conch shell). Then, the parents and others will do the same. Usually, only selected people like close friends and close relatives will be invited to the ROD-NAM-SANG event. If you are the immediate supervisor of the bride or bridegroom, you may be invited to join the ceremony. Accept it, it's a great honour. Please do not dress in BLACK colours (Dress and necktie). For Thais, the black colour is reserved for a sad event like a funeral. I have heard many Thais complained about foreigners wearing black dress to a wedding ceremony and it is a sign of bad luck to the bride and the bridegroom.
On the same night, there will be a wedding party.