While in Rome do as the Roman's do and when in a Thai restaurant why not try eating like the Thais?
Thai people enjoy dining as a larger group of friends when dish sharing is common so everyone gets to experience a wide range of flavours and spices. So, the main thing to do if you want to eat like a Thai is to head down to the Thai Orchid with a group of friends and order several dishes then put them in the centre of the table and help yourself to a bit of one and a bit of the other. Why not ask everyone to order their favourite dish and give a quick description of why it's their favourite for example what flavours they pick up or any memories it conjures up. It's a great talking point for the evening and helps everyone share something they like.
To really go with tradition you could ask the most senior lady in your dining party to order the dishes (if it won't get you in too much strife!) as traditionally this is he way a meal would be ordered.
Rice is a staple in a Thai meal so be sure to order some rice to go with any main dishes. Soup is normally seen in any Thai meal too so as a rule of thumb order several main dishes (currys etc) plus rice and soup
When it comes to desserts these are normally order per person and do not have to be shared (who wants to share a pudding?!) so you can keep your Khao Niaw Ma Muang all to yourself.
If you really want to experience a Thai meal the way a Thai would then try eating with just a fork and spoon. Thai food generally comes cut into small pieces to allow you to eat with a spoon without the need for cutting up the food with a knife. The fork is used to push food onto the spoon (which is held in the right hand) and it's considered bad manners to eat directly from the fork. It can take some getting used to when you've spent your whole life using a knife and fork but it's perfectly acceptable in a Thai restaurant so why not take the opportunity to try it next time you're in?
Above all, when you are eating like a Thai then the object is to enjoy the food, have a really social time, sample lots of flavours and spices and most importantly, to have fun.