All the lads in our gym have an on going jibe about the length of my Ram-Muay!!
It can last up to about 5mins! I was amazed at Orono Majestics ram-muay, it is brilliant. I think he won best Ram-muay award last year (?Rob?).... and he takes about 8mins!!!
I learnt mine in Thailand under the instruction of Jitti Damriram. He told me all about the mental thought that goes in to the symbolizm of the three bows etc (parents, teacher, god) and most of the thai mythical creatures the Ram-Muay immitates. It is a good stretch/warm-up... calm before the storm...

If a young boy wanted to be a fighter in Thailand he can spend up to 3/4 months learning the Ram-muay/wai-kru before even touching the pads!!!
Also, the first time I fought over there, all the guys in the gym came and asked me the next day, NOT how the fight went, but they were more concerned about the ram-muay.... I think this is from the adage "good wai-kru, good fight"...
This is probably the experiance which has put more impetus and value in to the wai-kru than the purely "western" philosophy of it "just being a warm-up"... I think, if you believe in it, it helps.... certainly has with me so far!!!

On the physical side, in high tense situations you sometimes see fighters become paralized by the situation in front of them, the ram-muay will serve as a "mobilisation" technique to get them thinking of the task in hand and drag them out of that paralysis before the fight.

I think its also part of the show! Giving a good ram-muay is similar to the Haka Maori's do, and I think spectators like to see that. It is also a good way of keeping hold of the Thai culture so it doesnt keep getting "watered-down" (although it is normally edited out of TV shows)