I have many Thai friends, and that's a tough one as everyone has their own preference/taste. You may not go wrong with a gift card from Crate & Barrel, Macy's, Home Goods (depending on what you think their taste is). It wouldn't be insensitive to give a gift card. This is because the fun of it all is that they get to pick and choose what they'd like. Another possible idea, various picture frames.

Above all, if still in doubt....whatever YOU choose is what they will appreciate because it's a gift from you.

Just get them a toaster, would you go out of your way for others? Would you buy Mexicans taco holders, or a deep fryer for black people? How about a rice cooker for Chinese people, pint glasses for Irish people, a pasta maker for Italian people, a Spam cook book for Hawaiians, or lube for gays? I don't think you would do this, so don't go out of your way to get them something special. For the record I'm Irish and would deck you if you got me pint glasses just because I'm Irish, especially if I had a few drinks. Besides I already have pint glasses.

it's more thoughtful to buy them a western gift than a thai gift. it expresses that you see beyond their nationality and view them as you would anyone else.

They always have lots of arrangements of artificial flowers; seldom real flowers, and they keep them.Even in big mansions having extremely wealthy people, they seem to like the artificial flowers. Most houses have lots of framed pictures, as well, so picture frames would be appropriate.

Many things would be appropriate, towels, plants, etc., but for a "traditional" Thai family a toaster would be as useless as t*ts on a board. I think you are being considerate in asking what culturally they would like.

And for some of the other answerers, they are mixing culture and races. And to give a race specific gift (like a deep fryer) might be considered an insult unless you knew the family wanted/needed one.