I hate to disagree, but flowers are not the right gift. (Usually, you only take flowers to a funeral.) I know this sentiment has changed lately in BKK, but I think fruit and other foods are always more acceptable.

Oh, and after living in Asia so long, I would be totally ashamed to arrive at someone's home (on invitation) without at least some token gift, even if it is only a bag of Bt20 fruit.

May I add my 2 stangs here.

There are many ways to do with the flowers not just for funeral only. Visiting someone in a hospital is a very nice gesture, it brighten up the room and lifting up the patient's spirit. When ever I'm invited to someone's house for birthday/wedding anniversary celebrating, I always make sure that I have an order of flowers to be delivered to the party. If I go as a guest at dinner, I would show up with a bottle of wine ( although I'm a none-drinker).

I would budget how much I plan to spend of these gifts accordingly on the place of the party and status of my hosts.

Be safe, bring condoms.

I would suggest bringing a small gift for the restaurant's "Spirit House" or the little Buddha shrine they will most likely have somewhere inside.

Or buy one of those gold cat statues that have the one arm waving up and down. They are supposed to be good luck.

Knowing that the woman is married, I would shy away from flowers. Some people may get the wrong idea about why you are giving her flowers (and the other staff in the place will surely have their tongues wagging).

If I had a restaurant and someone I invited brought food/booze with them, I might be a little offended (after all, what's wrong with the food/booze I'm serving, that you feel the need to bring your own in ? )

If it is expected that you are going to be paying for the meal any ways, bringing your own stuff in may be seen as an attempt to reduce the amount spent in that place.