That said, there are lucky exceptions. I saw an advert for this place in London's Thai-language newspaper. It is normally a sure-fire sign of authentic fare.
My gut was right. North-Eastern sausages (krok Lao) were perfectly done: crunchy on the outside, juicy and spicy inside. The sticky rice was expertly cooked. And the yam (a kind of spicy escoveche) of raw crab was nothing short of revelation. I have never had anything like that even when I lived in Thailand.
It was hard to do it all justice though, as the waiters refused to turn down the blaring karaoke, despite there was no other clients in the restaurant. Cheesy tunes were echoing unobstructedly in the empty room full of garishly bright plastic tables and chairs, bouncing off the walls into our poor ears. Very soon our throats got sore from trying to outshout the electrically amplified voices of Thai pop stars and we just kept drinking water that was pushed on us at a pound a bottle against our will.
Pro's: Fantastically tasty food.
Con's: Obnoxiously noisy. Horrible interior. Rude sour service. Pricey.
In a nutshell: Thai food connoisseur's paradise if you know how to switch all your other sense but the taste.