Hi authentic Thai food is generally pretty sw friendly, as they use stock instead of oil to cook with and lots of veggies! I'd go for something like a phad Thai (noodle based with veg) or a fried rice type dish. The curries tend to use coconut milk which would by quite synful I suppose, and avoid anything deep fried/battered! X
Sounds good simple steamed/boiled rice would be free on an EE day so you could eat as much as you wanted! I'd say your syns would be in the sauce but in oyster they should be minimal since its not particularly sweet. Hope you enjoyed it! X