In the past and until today Thai girls often forgo the official marriage registration for a variety of reasons, in particular because they loose many legal civil rights.
Instead, thai girls are conducting a traditional Thai wedding ceremony.
For the Buddhist religious beliefs, most Thai girls (and especially the parents) would be very happy to have a marriage ceremony of traditional Thai wedding, albeit the fact that it is not legally recognized as a marriage.
According to Thai customs, a couple traditionally become engaged during a ceremony known as 'Thong Mun'.
This is literally the giving of gold by the prospective groom to his thai fiancee.
Parents, friends and relatives will attend this ceremony.
In place of a diamond ring as common in the West, Thai girls opt for the gold, normally in the form of jewelery.
Actually, it is almost 96% pure gold made in Thailand. When traded locally, its weight is measured in 'Baht'.
One Baht of gold is equals to 1/2 a troy ounce or 15.2 grams.
In practice, an odd number is never given as it were for a couple), so the minimum should be two Baht of gold.
This marriage is taken quite seriously by all concerned, and regarded as a lifelong commitment made by the couple.
In the eyes of the Buddhist religion, the marriage is recognized and sacred, albeit the fact that in contrast to other religions, a religiously sanctioned marriage is void in Buddhism.
Traditional Thai marriage ceremonies and rituals need not be conducted in the presence of monk and are usually performed at someone’s home.
Following the chanting ceremony which if you have a foreigner as best man?
One can say a few words in English and then the wrists are tied etc & the house is blessed. The ceremony concludes after approx1/2-1 hour and then the monks will eat before the guests.
The monks do not stay after they eat and leave as it is not polite to watch foreigners drinking.
Simply put, there is no such thing as the Buddhist wedding ceremony, and if the monks are present at wedding, they are not directly involved.
If the monks are invited (which is happening quite often), there always should be an odd number: 3, 5, 7 and the maximum could be 9 monks.
A good number is say 3 or 5. One must allow for presents for 4 if 3 monks or 6 if 5 monks.
The 4th & 6th vacancy is buddha so offering to them can be in the form of money in an envelope, towels, books etc for each of the 4in similar parcels.
According to the Thai faith, to assure a "lifetime of love" marriage, there is an old Thai ritual of "merit gift" -- a donation to the local Wat (Buddhist temple) to perform a wedding ceremony.
Even it is not directly related to marriage, a merit-making ceremony would mean a lot to the thai bride-to-be and in turn to a thai girls family, to have a gift made in their name by you.
It shows that you care about her religious beliefs, value the Thai ways and respect Thai culture.